Voters in Arizona will cast their ballots in a slate of primary elections Tuesday, including a Republican primary for what will be a hotly contested Senate seat that could help determine which party controls the chamber next year.

Perhaps the most closely watched primary in the state will be the race for the Republican nomination to replace Sen. Kyrsten Sinema (I), who left the Democratic Party in 2022 and announced earlier this year that she would not seek reelection to a second term. The winner of the GOP primary will advance to the general election to face Rep. Ruben Gallego (D), who is uncontested in the Democratic primary.

There are also competitive primaries for two of the state’s largest congressional districts, including one that Democrats see as an opportunity to flip a House seat and another that will pit two top allies of former president Donald Trump against one another.

Senate Republican primary

Former television anchor Kari Lake, who ran for Arizona governor and lost in 2022, is considered the front-runner in the GOP primary race for Senate, which also includes Pinal County Sheriff Mark Lamb and Elizabeth Reye, a neuroscientist who has positioned herself as a “Reagan Republican.” Trump has endorsed Lake, who has echoed Trump’s false claims that widespread voter fraud cost them their elections.

The winner of the GOP primary will advance to the general election to face Gallego, who has been running ads attacking Lake as his presumptive opponent nearly since he launched his campaign.

The GOP primary has polarized Republicans in the state, who remain divided between those who are staunch supporters of Trump and those who consider themselves more in the mold of the late Arizona senator John McCain, a conservative who also rejected Trumpism.

For instance, Randy Kendrick — a conservative activist who is one of Arizona’s top GOP donors and is married to the owner of the Arizona Diamondbacks — recently sent an email to her entire “Christmas card list” telling people that Lake “cannot win the general election” in Arizona and urging them to vote for Lamb instead. Lake lost the 2022 gubernatorial race to now-Gov. Katie Hobbs (D).

1st District Democratic primary

A crowded field of Democrats is competing to take on incumbent Rep. David Schweikert (R) in what is likely to be the state’s most competitive race in November. Arizona’s 1st Congressional District is sprawling, covering much of northeastern Phoenix as well as the wealthy suburbs of Scottsdale, Paradise Valley, Cave Creek and Fountain Hills.

The half-dozen Democratic candidates vying for the party’s nomination include business executive Andrei Cherny, former television anchor Marlene Galán-Woods, orthodontist Andrew Horne, business executive Kurt Kroemer, lawyer Conor O’Callaghan and former state representative Amish Shah. No clear front-runners have emerged.

The winner of the Democratic primary will advance to the general election to face Schweikert, who has served in the House for nearly 15 years. He was first elected to Congress in 2010, and he has won reelection — in various redrawn districts — several times since, though his margins of victory have decreased over the years. Schweikert narrowly won reelection in 2022 by less than one percentage point, and Democrats have targeted his seat as a possible pickup.

8th District Republican primary

A half-dozen Republican candidates are competing in the GOP primary to replace Rep. Debbie Lesko (R), who announced in October that she would not seek reelection after the end of her term. Arizona’s massive 8th Congressional District covers much of north Glendale and the West Valley suburbs of Peoria, Sun City and Sun City West, and stretches all the way north to Lake Pleasant and New River.

Front-runners for the GOP primary include several prominent figures in the state party: former Senate candidate Blake Masters and former state attorney general candidate Abe Hamadeh — both of whom lost their respective races in 2022 to their Democratic opponents. In an unusual circumstance, both also have the support of Trump, who hedged his bets with a last-minute dual endorsement.

“They will both be spectacular, and I’m pleased to announce that both Blake Masters and Abe Hamadeh have my Complete and Total Endorsement to be the next Congressman of Arizona’s 8th Congressional District — THEY WILL NOT LET YOU DOWN!” Trump wrote Sunday in a post on his social media platform.

Also running in the GOP primary are Arizona House Speaker Ben Toma, former congressman Trent Franks — who previously represented this district — and Arizona state Sen. Anthony Kern.

Yvonne Wingett Sanchez contributed to this report.