Joseph I. Lieberman, the doggedly independent four-term U.S. senator from Connecticut who was the Democratic nominee for vice president in 2000, becoming the first Jewish candidate on the national ticket of a major party, died March 27 in New York City. He was 82.

The cause was complications from a fall, his family said in a statement.

Mr. Lieberman viewed himself as a centrist Democrat, solidly in his party’s mainstream with his support of abortion rights, environmental protections, gay rights and gun control. But he was also unafraid to stray from Democratic orthodoxy, most notably in his consistently hawkish stands on foreign policy.

His full-throated support of the 2003 invasion of Iraq and the increasingly unpopular war that followed doomed Mr. Lieberman’s bid for the Democratic presidential nomination in 2004 and led to his rejection by Connecticut Democrats when he sought his fourth Senate term in 2006. He kept his seat by running that November as an independent candidate and attracting substantial support from Republican and unaffiliated voters.

“I have not always fit comfortably into conventional political boxes,” Mr. Lieberman said near the end of his Senate career, an understatement that tiptoed around the anger his maverick ways stoked among many liberals.

His transition from Al Gore’s running mate in 2000 on the Democratic ticket to high-profile cheerleader for Republican presidential candidate John McCain eight years later was a turnaround unmatched in recent American politics.

In a prime-time speech at the 2008 Republican convention, Mr. Lieberman hailed McCain, a senator from Arizona and former Vietnam War POW, for his courage and accomplishment. He dismissed Barack Obama, the one-term senator from Illinois and Democratic nominee, as “a gifted and eloquent young man” who lacked the experience needed in the White House.

On international trips to Iraq and other hot spots, Mr. Lieberman and McCain had become close friends as well as allies in support of the Iraq War — including President George W. Bush’s decision in 2007 to shore up the faltering U.S. military effort with the “surge” of thousands of additional troops.

McCain seriously considered making Mr. Lieberman his running mate, but his advisers warned that Mr. Lieberman’s Democratic history and voting record, particularly his stand in favor of abortion rights, would anger convention delegates and split the party. McCain instead chose the right-wing populist governor of Alaska, Sarah Palin, a decision he later said he regretted.

Most observers, including Mr. Lieberman, doubted that his presence on the ticket would have saved McCain from defeat by Obama, who became the first Black president. Mr. Lieberman remarked that had he joined McCain on the ballot, he would have had the distinction not only of running for vice president on both party tickets but also of losing twice. “God saved me from that — or the Republican delegates saved me from that,” he told the Hartford Courant.

Mr. Lieberman continued to draw Democrats’ ire after leaving the Senate in 2012, most especially with his efforts to mount a third-party presidential ticket in the 2024 election. As a co-chair of the centrist group No Labels, he helped lead the organization’s campaign to field an alternative to the major-party candidates — a move that some Democrats feared would take votes from President Biden and help Donald Trump recapture the White House.

Joseph Isadore Lieberman was born in Stamford, Conn., on Feb. 24, 1942, the oldest of three children in an Orthodox Jewish family. His father, a former bakery-truck driver, eventually saved enough to buy a liquor store. His parents impressed upon him the value of education and instilled in him an ambition to succeed. He was senior class president and senior prom king of his high school.

He entered Yale University in 1960 as the first member of his family to go to college, and he said he was inspired to enter public service by President John F. Kennedy’s inaugural address, with its challenge to “ask what you can do for your country.”

While in college, he worked part time on the successful 1962 U.S. Senate campaign of Abraham Ribicoff, a former Democratic congressman and governor, and the next year was a summer intern in Ribicoff’s Washington office. Ribicoff, the son of Jewish immigrants from Poland, became a role model and taught him, Mr. Lieberman wrote, the value of compromise over unproductive rigidity.

Mr. Lieberman furthered his political education by writing his senior thesis on John M. Bailey, a backroom pol who had long dominated Connecticut’s Democratic Party and served as chairman of the Democratic National Committee for much of the 1960s. The thesis resulted in a Bailey biography, “The Power Broker” (1966) — the first of nine books Mr. Lieberman wrote or co-wrote. In addition to lessons-learned memoirs, the subjects ranged from nuclear proliferation to the benefits of resting on the Sabbath.

After graduating from Yale in 1964 and then Yale Law School in 1967, he joined a New Haven firm, became active in local political and community work, and looked for an opportunity to run for office. It came in 1970 when he upset the incumbent state senator from largely Democratic New Haven in the party primary. Among his doorbell-ringing volunteers was Bill Clinton, then a Yale Law student.

Mr. Lieberman served 10 years in the state Senate, the last six as majority leader. His ambition was to be governor, but, in 1980, seeing no immediate path to higher state office, he gave up his Senate seat to run for the open U.S. House seat for the New Haven area.

With the district’s Democratic advantage and strong polling numbers, his victory seemed assured. But helped by Ronald Reagan’s strong showing in the presidential race, the Republican won. The loss was painfully embarrassing for a politician unused to defeat. Not long afterward, in 1981, he and his first wife, Elizabeth “Betty” Haas, divorced.

In Mr. Lieberman’s telling, he and his wife — the parents of two children, Matt and Rebecca — drifted apart as their personalities and careers developed. The demands of his political life were one factor, he wrote in his 2000 memoir, “In Praise of Public Life.” Another was “that I had become much more religiously observant.”

A year after the divorce, a friend introduced him to Hadassah Freilich Tucker, a Prague-born daughter of Holocaust survivors whose father was a rabbi. Her family — the Freilichs — immigrated to the United States in 1949 after the Communists took over Czechoslovakia. When Mr. Lieberman met her, she was the divorced mother of a 6-year-old son, Ethan, and an executive at Pfizer Pharmaceuticals in New York City. It was, Mr. Lieberman wrote, “chemistry at first conversation.”

They married in 1983, and she was her husband’s political partner and trusted adviser through the rest of his career. In addition to his wife, survivors include their daughter, Hana Lowenstein; two children from his first marriage, Matt Lieberman and Rebecca Lieberman; a stepson, Ethan Tucker; two sisters; and 13 grandchildren.

In 1982, ready for another try, Mr. Lieberman ran for what had been the low-profile office of state attorney general. Promising to be the “people’s lawyer,” he swept to victory — along with the other Democratic candidates for statewide state offices — and built an activist record by going after polluters, consumer rip-offs and child-support delinquents.

He easily won reelection four years later, and then, urged on by party leaders, he took on U.S. Sen. Lowell P. Weicker Jr., a three-term liberal Republican generally thought to be unbeatable. With TV attack ads and support from Republicans unhappy with Weicker — including an endorsement from prominent conservative intellectual William F. Buckley Jr. — Mr. Lieberman squeaked to victory in 1988.

In Washington, Mr. Lieberman became known as a serious-minded legislator adept at working with colleagues on both sides of the aisle. One of his earliest achievements was having a leadership role in the bipartisan amendment in 1990 of the Clean Air Act, beefing up federal regulation of pollutants.

He was also proud of bipartisan government changes he helped enact after the Sept. 11, 2001, terrorist attacks, most prominently the creation of the Department of Homeland Security and the restructuring of the intelligence community.

Mr. Lieberman generally voted with his party, but he sided with Republicans on cutting the capital gains tax, funding vouchers that parents could use to send their children to private schools, and placing new restrictions on consumer lawsuits against corporations, the latter of special interest to Connecticut’s large insurance companies.

His willingness to buck his party put him at odds with teachers, trial lawyers and other powerful Democratic constituencies. But it gave him influence within the increasingly polarized Senate, former Senate historian Donald Ritchie said in an interview for this obituary. As the political middle shrank, his swing vote took on added value.

In the run-up to the Iraq War, a majority of Senate Democrats voted to authorize Bush to take military action against Saddam Hussein’s regime. But unlike many of those colleagues, Mr. Lieberman continued to support the 2003 invasion after Hussein’s alleged weapons of mass destruction failed to materialize and U.S.-led occupation forces were bogged down by civil war and anti-coalition insurgency.

“This is a battle in the war on terrorism. Failure and defeat is not an option,” he said in September 2003. When Senate Democrats voted unanimously in April 2007 to begin withdrawing U.S. troops by the following October, he joined Republicans in opposition.

His stand was in keeping with a long record of support for intervention abroad. He co-sponsored the resolution authorizing the use of troops to expel Iraqi forces from Kuwait in 1991 and pressed the Clinton administration to take forceful action against Serbian aggression in the Balkans. He was one of Israel’s most fervent backers on Capitol Hill. And, in line with the interests of Connecticut’s large defense industry, he supported robust spending on weaponry.

“Like it or not, we live in an imperfect world, so, like it or not, you’ve got to stand up and fight,” he told the New York Times in 1991. “If I can be simplistic about it: If good people stand by while bad things are being done, evil will triumph.”

In private life, Mr. Lieberman was a strict observer of Orthodox Jewish rules. He kept a kosher diet, prayed daily and declined to campaign on the Sabbath. He brought moral certitude to his public life as well, denouncing gratuitous sex and violence in films, television shows and pop music.

He helped enact a 1996 law requiring new TV sets to have a device that enabled parents to block objectionable programs, and he teamed up with conservative commentator William J. Bennett to hand out “Silver Sewer Awards” for media content deemed “cultural pollution.” Along with headlines, Mr. Lieberman garnered loathing from the entertainment industry. “He’s a self-righteous religious fanatic,” record company executive Howie Klein said in 2000, as quoted on MTV.com. Television critic James Poniewozik, then with Time magazine, dubbed him “Schoolmarm Joe.”

Mr. Lieberman cemented his reputation for diligent morality — or moralizing, as his detractors saw it — in 1998 when he publicly rebuked President Clinton, a personal friend and fellow Democrat, for his affair with White House intern Monica Lewinsky. He was the first prominent Democratic lawmaker to do so.

“Such behavior is not just inappropriate. It is immoral,” he said in a Senate speech that drew praise from colleagues in both parties. “And it is harmful, for it sends a message of what is acceptable behavior to the larger American family — particularly to our children — which is as influential as the negative messages communicated by the entertainment culture.” (In 1999, Mr. Lieberman joined all other Democratic senators in voting against removing Clinton from office.)

For Gore, Clinton’s vice president, the Lewinsky speech and, more broadly, Mr. Lieberman’s rectitude made him a particularly attractive running mate at a time when Gore was anxious to distance himself from Clinton’s tawdry personal conduct.

At the campaign’s outset, there was speculation that antisemitism, latent or overt, might hurt the Gore-Lieberman ticket. Mr. Lieberman embraced his faith in public, often quoting from the Hebrew Bible and giving thanks to God. The Anti-Defamation League asked him to reduce his religious references during the 2000 race to avoid alienating the public.

One of Mr. Lieberman’s enduring themes was that religion in general, not just the Jewish faith, deserved a more prominent place in public life. Years later, Mr. Lieberman told CNN that he encountered no antisemitism on the campaign trail. And the consensus among pundits was that Mr. Lieberman’s religion played no role in Gore’s loss, in keeping with political history that suggests a party’s vice-presidential choice seldom makes a difference in the voting.

Gore and Mr. Lieberman lost the election to Bush and his running mate, Dick Cheney, following a 5-to-4 Supreme Court ruling that awarded Florida’s disputed 25 electoral votes to the GOP ticket. But Mr. Lieberman emerged with national name recognition and, once Gore declined to run again, front-runner status in early polling for the party’s 2004 presidential nomination.

Considered the most moderate of the party’s nine 2004 hopefuls, Mr. Lieberman contended that his record on the environment and social issues combined with his strong stand on defense made him the Democrat best positioned to attract independents and defeat Bush.

What pundits described as a dearth of cash and charisma worked against him. Gore’s endorsement of another candidate, former Vermont governor Howard Dean, was a further blow. But the biggest obstacle to Mr. Lieberman’s nomination was the anger among Democrats over his support of the Iraq War.

He placed fifth in the New Hampshire primary, and the following Tuesday, the best he could do in seven state nominating contests was a distant second in Delaware. It was an unmistakable repudiation, and Mr. Lieberman dropped out that night. (Sen. John F. Kerry of Massachusetts eventually won the nomination and lost the general election to incumbent Bush.)

Mr. Lieberman’s defeat two years later in the Democratic Senate primary in Connecticut was an even more painful measure of his party standing. His challenger, wealthy businessman (and later governor) Ned Lamont, focused on Mr. Lieberman’s support of Bush’s war policy and made heavy use of a photo of the president embracing Lieberman at the 2005 State of the Union speech.

Mr. Lieberman, who had breezed to reelection twice before, dismissed the primary’s outcome as unrepresentative of the state’s full electorate and, running as an independent in the general election, got almost 50 percent of the vote, to Lamont’s 40 percent and 10 percent for the little-known GOP nominee. Mr. Lieberman later disclosed that a top Bush aide steered GOP money to his campaign.

Returning to the Senate as a self-described “independent Democrat,” Mr. Lieberman continued to caucus with the Democrats. But he viewed his November victory as vindication of his independent record and felt, as he put it, “profoundly liberated.”

For some Democrats, Mr. Lieberman’s support of McCain two years later went beyond independence to apostasy. After the election, there was a move to strip him of his chairmanship of the Homeland Security and Governmental Affairs Committee. But party leaders were anxious to keep him from bolting to the Republicans.

After Obama and Democratic Senate leader Harry M. Reid of Nevada urged forgiveness, Senate Democrats voted 42 to 13 to let Mr. Lieberman keep the chairmanship. His only penalty was the loss of his seat on the Environment and Public Works Committee. He accepted the arrangement, telling reporters that he regretted some of his campaign statements “and now it’s time to move on.”

In 2009, he helped the new Obama administration get its first big win: a $787 billion package to stimulate the recession-racked economy. The next year, he was a leader in the successful fight — against GOP opposition led by McCain — to repeal the Clinton-era “don’t ask, don’t tell” policy prohibiting gay people from serving openly in the military.

He was also influential in shaping Obama’s health-care initiative, although in a way that once again infuriated some Democrats. Attentive to Connecticut’s insurance industry, Mr. Lieberman threatened to filibuster the bill if it included a government-run health insurance option. With the support of every Senate Democrat needed to overcome solid GOP opposition, the administration dropped the public option, and Mr. Lieberman voted in 2009 for the Affordable Care Act, also known as Obamacare.

Mr. Lieberman announced in early 2011 that he would not seek reelection the next year. By way of explanation, he invoked Ecclesiastes. It was, he said, “time for another season and another purpose under heaven.” He dismissed poor political prospects as a factor. He conceded that he faced a difficult campaign but added, “So what else is new?”

After leaving the Senate, Mr. Lieberman became senior counsel at the Manhattan-based law firm Kasowitz, Benson, Torres and joined company boards. He continued to take public positions on political issues. He led a group opposed to the Iran nuclear deal negotiated by the Obama administration. He endorsed President Donald Trump’s decision to move the U.S. Embassy in Israel to Jerusalem. He promoted Trump’s nomination of Betsy DeVos, a charter school and voucher advocate, to be education secretary.

Nevertheless, Mr. Lieberman endorsed the Democratic presidential nominees in 2016 and 2020 — Hillary Clinton and Joe Biden, respectively — and told CNN in 2021 that Trump was “really hurting our constitutional democracy” by continuing to claim the 2020 election had been stolen.

He was most prominent as a leader of No Labels, an organization founded to encourage bipartisanship, and he missed no opportunity to reiterate the plea he made in his 2012 farewell Senate speech. “The greatest obstacle I see standing between us and the brighter American future we all want is right here in Washington,” he told colleagues. “It is the partisan polarization of our politics which prevents us from making the principled compromises on which progress in a democracy depends.”