Democrats on Thursday began the process of making Vice President Harris their formal presidential nominee on a day that saw several campaign developments and highlighted one of the solemn challenges of an American president: bringing hostages home.

Democratic delegates began online voting Thursday in a process that almost certainly will result in Harris formally becoming the party’s nominee, since she is the only candidate who qualified and most of the delegates have already endorsed her. Yet her official selection will mark a significant milestone, making her the nation’s first Black woman to become a major-party presidential nominee and capping one of the most tumultuous months in recent American political history.

Parties typically nominate their ticket at their in-person convention, but Democratic leaders were concerned that early ballot deadlines in several states could make it risky for them to wait until the Democratic National Convention on Aug. 19-22. They set up a virtual nomination process that started Thursday morning and could last until Monday, though Harris could clinch the nomination sooner.

Harris is expected to name her running mate in the coming days before launching a joint nationwide campaign tour starting Tuesday across seven battleground states. The campaign has announced that Harris and her running mate will travel to Philadelphia; Eau Claire, Wis.; Detroit; the Research Triangle in North Carolina; Savannah, Ga.; Phoenix; and Las Vegas.

There was no indication of a final decision Thursday, but strategists on both sides were carefully watching the actions of the Democratic figures who have been mentioned as potential running mates.

Pennsylvania Gov. Josh Shapiro (D) has canceled some upcoming appearances in what could be read as a schedule-clearing move to join Harris. But a spokesman said the governor’s trip this weekend to the Hamptons on Long Island, which was planned “several weeks ago and included several fundraisers for his own campaign committee,” was canceled because “his schedule has changed.”

Sen. Mark Kelly (D-Ariz.) on Thursday attacked former president Donald Trump’s recent comments about Harris’s racial identity. “It’s such a desperate, desperate attempt to rebuild his campaign that’s obviously faltering,” Kelly told reporters in the U.S. Capitol. “She’s the person to bring us into the future, and Donald Trump is about divisiveness.”

At an event Wednesday hosted by the National Association of Black Journalists, Trump said he “didn’t know [Harris] was Black until a number of years ago when she happened to turn Black and now she wants to be known as Black.” He added, “Is she Indian, or is she Black?”

Kelly declined to comment on reports that he met with Harris’s vetting team in the past few days. “This isn’t about me. This is about beating Donald Trump,” he said.

Other senior Democrats who are considered close to the Harris campaign and could be potential running mates are Kentucky Gov. Andy Beshear and Minnesota Gov. Tim Walz.

Harris on Thursday delivered a eulogy at a Houston service for the late Rep. Sheila Jackson Lee (D-Tex.), who died last month at age 74 after being diagnosed with pancreatic cancer.

She called her late friend “a change-maker” and a “coalition builder.” At one point, Harris misspoke and referred to herself as “president” before correcting to say “vice president” — triggering cheers from the crowd.

“It was Sheila Jackson Lee whose bill made Juneteenth a federal holiday,” she said, “which, as a United States senator, I was proud to co-sponsor. And then as president — as vice president — it was my honor with the president … [to make it into law]. It was my honor.”

On the Republican side, nominee Donald Trump’s campaign announced that the former president would participate in a rally in Bozeman, Mont., on Aug. 9. Montana is the site of a major battleground Senate race between incumbent Sen. Jon Tester (D) and Trump-endorsed Republican candidate Tim Sheehy, a former Navy SEAL.

Trump’s campaign also announced that it had raised $138.7 million during the month of July and had $327 million cash on hand. Harris’s campaign said it had raised $200 million during the first week of her candidacy. The figures cannot be confirmed until later this month, when financial disclosures are filed.

Trump did not hold any public events Thursday, but Sen. JD Vance (Ohio), the Republican vice-presidential candidate, delivered remarks at the U.S.-Mexico border in southeast Arizona.

Dressed in a flannel shirt, jeans and hiking boots, Vance greeted law enforcement authorities with handshakes and was shown a spot where the border wall — which Trump started building when he was president — was incomplete.

After 30 minutes of speaking with law enforcement officials and touring the border, Vance made comments in which he repeatedly criticized Harris and referred to her as the “border czar.” Harris and other Democrats have rejected that title, noting that Biden asked her to tackle the root causes of migration in El Salvador, Guatemala and Honduras, not to address illegal border crossings.

Vance described several policy initiatives that he said a Trump-Vance administration would implement, including resuming border wall construction, more aggressively deporting undocumented immigrants and investigating drug crimes further.

“It’s hard to believe, until you see it with your own eyes, just how bad the policies of the Kamala Harris administration have been when it comes to the southern border,” Vance said.

Vance also said he and the former president have a “good relationship” and sought to push back on criticism that Democrats — and some Republicans — have leveled against him since he was put on the ticket. Vance, for example, has come under fire for previously calling Democrats such as Harris “a bunch of childless cat ladies who are miserable.”

“Look, it’s the same thing they did to Dick Cheney, the same thing they did to Mike Pence,” Vance told NOTUS in an interview Wednesday, referring to past Republican vice-presidential nominees. “I think that any Republican who comes out of the gate as the new VP nominee is going to get attacked. I have no doubt that the president is confident in the way that I’ve been doing things.”

Vance said his “good relationship” with Trump “will keep on going through all the way to November — hopefully past that, too.”

The Ohio senator said he has no regrets over having been supportive of the Heritage Foundation and its Project 2025, a blueprint for an incoming conservative administration that Democrats have attacked and from which Trump has distanced himself.

“The Heritage Foundation has some good ideas, and also has some ideas that … I think are bad ideas,” Vance told NOTUS. “And regardless of whether you think they’re good ideas or bad ideas, it has nothing to do with the Trump campaign.”

Vance said he had not read the entire 900-page document. “There are some things I like about it, and some ideas in there that I strongly disagree with,” he said.

The organizers of Project 2025 recently announced that the initiative is winding down its policy operations and that its director, former Trump administration personnel official Paul Dans, is departing.

Amid the campaign activity, events unfolded Thursday showcasing the gravity of the office that Harris and Trump are seeking. Biden announced a complex release of hostages — including Evan Gershkovich and Paul Whelan, who were both held by Russia.

Biden made forceful remarks signaling that while he is no longer running for reelection, he intends to use the powers of his office to the fullest for the six months he has remaining in the office. Trump immediately questioned whether the deal was as beneficial to the U.S. side as it could have been.

Harris, who was in Houston for the memorial service, flew back to Washington to join Biden in greeting the hostages at Joint Base Andrews. She also spoke with Yulia Navalnaya, widow of Alexei Navalny, and welcomed the release of 16 individuals from Russia, including political prisoners who worked with Navalny.

“The United States stands with all of those who are fighting for freedom in Russia,” Harris said on the tarmac outside Air Force Two before flying back to Washington. “As we celebrate today’s news, we must also keep front of mind that there are other Americans that are unjustly being held in places around the world, and we will never stop fighting for their release.”

Meryl Kornfield, Mariana Alfaro, Liz Goodwin, and Amy B Wang contributed to this report.