GOP's Kari Lake and Democrat Ruben Gallego to face off in Senate race based on Arizona primary projections

Voters in Arizona went to the polls Tuesday, in the first congressional and down-ballot primaries since President Joe Biden dropped out of the presidential race and former President Donald Trump officially became the Republican presidential nominee.

The Associated Press has projected that Kari Lake will win the Republican primary for U.S. Senate in Arizona.

With 66% of the expected vote reporting as of 11:46 PM, Lake leads with 53.3% of the vote. Mark Lamb has 40.6%.

Lake goes on to face U.S. Rep. Ruben Gallego, who was unopposed in the Democratic primary, in the general election – in a race certain to be closely watched in the battleground state. Whoever wins will take the seat currently held by retiring independent Sen. Kyrsten Sinema.

"Thank you for putting your faith in me, Arizona. I won't let you down. Together, we're going to save this state. Together, we're going to #MakeArizonaGrandAgain," Lake wrote in a post on X.

In a statement on Tuesday night, Gallego wrote, "From now until November, I welcome all Arizonans — Democrats, Republicans, and Independents alike — to join our team and help defeat Kari Lake and her dangerous plan to ban abortion and hurt Arizonans."

When Sinema announced in March that she would not seek reelection, she set up a likely matchup to replace her between Republican Lake and Democratic Rep. Ruben Gallego.

In the Republican primary, Lake faced a few primary opponents, most notably Pinal County Sheriff Mark Lamb.

Lake, a former local news anchor, has become known in part for her outspoken support of Trump's false claims of voter fraud. Her Senate campaign comes after she narrowly lost her bid for governor to Democrat Katie Hobbs in 2022, after which she refused to accept the results of the race.

As she campaigned for office in 2024, Lake noticeably softened her stance on mail-in voting, which Trump attacked after he lost the 2020 presidential election.

Speaking in March, Lake encouraged Arizonans to vote "whether that's by mail, whether you vote in person." She added, "We can't throw our hands up and say the system doesn't work. Of course it doesn't. But we need to get out and get more people to vote."

However, speaking to a small group of reporters after her speech, Lake said: "I'd like to get back to Election Day, not election month, where we count the votes on Election Day and we know the results at night, but we're not in that world right now."

Lamb has also raised questions in the past about the results of the 2020 election, but said he found no evidence of fraud. He campaigned on border issues and had some fundraising support, but struggled to break through in the primary.

Lake has also faced consternation within the Arizona Republican Party. Now-former Arizona Republican Party Chair Jeff DeWit resigned in January after an audio recording was leaked that reportedly contained him asking Lake to name a price that would keep her out of politics. DeWit said the recording was "selectively edited."

More recently, the Washington Post reported that a major Republican donor in the state wrote that Lake "cannot win the general election."

On the Democratic side, Gallego was the only candidate running for the seat.

Republican primary in Arizona's 8th congressional district

In Arizona's 8th congressional district, the race to replace Republican Rep. Debbie Lesko, who announced in October that she will not run for reelection, became exceptionally contentious. As of midnight Eastern on Wednesday, the Associated Press had not yet made a projection in the race.

Masters, a protégé of venture capitalist Peter Thiel who was previously defeated by Democratic incumbent Mark Kelly in the race for one of Arizona's senate seats, faced off against Hamadeh, who ran for Arizona attorney general and lost by just 280 votes. The primary's winner is likely to win the seat in the highly Republican district's general election.

The race has been filled with personal attacks. American Principles Project, a Super PAC supporting Masters, ran an advertisement about Hamadeh targeting his Muslim faith, calling Hamadeh a "terrorist sympathizer" and claims that he has said that "America was founded on Islamic principles, not the Judeo-Christian values that made America great."

In a website constructed to share opposition research, Masters' campaign shared what they claim to be a post by Hamadeh, in which the author argues against the demonization of Muslims by referring to the presence of Muslim influence in American iconography in law. A review by the Phoenix New Times supported Masters' suggestion that Hamadeh was responsible for the account.

Masters also released texts he shared with Hamadeh in January 2023 while Hamadeh was contesting the results of his election. In the messages, Hamadeh derides some who question election integrity, saying he was glad he wasn't "lumped in with crazies with election stuff … but the crazies love [me] because they see me fighting."

In statements to the Arizona Republic, Hamadeh's spokesperson Erica Knight called the attacks on "falsehoods and vicious lies that go beyond the pale."

Hamadeh has also gone on the attack, making unfounded claims that that Masters "lived in a nudist vegan commune" and "played on the women's college basketball team" while at Stanford University and calling him a leftist.

Ryan Girdusky, a spokesperson for Masters responded to the attacks, saying to the Arizona Republic that Hamadeh is "narrating to voters quotes from Blake, or old quotes about Blake, or life experiences from Blake that are not true."

Some additional intrigue has come from endorsements by the Republican ticket for president. Though Trump endorsed Masters in 2022, for much of the race, Trump had only endorsed Hamadeh in the race, a fact that Hamadeh's campaign touted. Trump's vice presidential candidate, Ohio Sen. JD Vance, endorsed Masters in October.

But in a shock twist on Sunday, Trump added an endorsement for Masters.

Rep. Trent Franks, State House Speaker Ben Toma and State Sen. Anthony Kern are also ran for the seat.

ABC News' Olivia Rubin, Soorin Kim, Lalee Ibssa, Kelsey Walsh, and Hannah Demissie contributed to this report.