(CNN) In one of next year's most consequential Senate races, the Republican primary to take on Democratic Sen. Mark Kelly of Arizona is turning on a question: Who won the 2020 presidential election?
Former President Donald Trump's false claims of widespread voter fraud, including his promotion of a controversial, partisan audit of the vote in Maricopa County, has dominated the debate within the Arizona GOP for months, as it recovers from Trump's and Republican Sen. Martha McSally's close losses to Joe Biden and Kelly last year.
While some Republican Senate candidates say they have accepted Biden's victory in Arizona and in the Electoral College, others have continued to question it -- defending the ongoing, Republican-driven audit in Maricopa, which is home to Phoenix and nearly two-thirds of the state's vote -- and called for "election integrity" measures.
They are vying for the chance to oust Kelly, the former astronaut and fundraising powerhouse who is seeking a six-year term in 2022.
The newest entrant into the GOP Senate primary is Blake Masters, a 34-year-old venture capitalist and protege of tech billionaire Peter Thiel, who officially announced his candidacy this week. Thiel is expected to spend $10 million on a Super PAC supporting Masters' campaign.
In an interview with CNN on Tuesday, Masters said so-called election integrity "may be the top priority" of his campaign and said, "it's really hard to know" who won the presidential race. Masters said he believed Biden is president since he was sworn-in and certified by Congress but that the election raised questions.
He joins a Republican field that already includes Arizona's attorney general Mark Brnovich; solar-energy entrepreneur Jim Lamon; and retired Maj. General Michael "Mick" McGuire, the state's top National Guard officer who also headed Arizona's emergency response department during the pandemic. All of them have embraced some level of rhetoric about shoring up confidence in US elections.
But some Republicans are worried that embracing Trump's falsehoods could hurt their eventual nominee in the party's effort to take back the Senate in 2022.
"The audit is an albatross around the neck for every Republican running in the state of Arizona," said Chris DeRose, the former clerk of the superior court in Maricopa County and a Republican lawyer.
As Arizona's top law enforcement officer, Brnovich has claimed early frontrunner status among operatives in the state, boosted by his 6-3 victory at the Supreme Court to uphold Arizona law discarding in-person ballots cast at the wrong precinct and restricting "ballot collection" requiring that family caregivers, mail carriers and election officials can deliver another person's completed ballot to a polling place. He has also sued the Biden administration over its immigration policies and secured multi-million dollar payments for consumers in cases against telecommunications company CenturyLink, electric utility Arizona Public Service Company and General Motors.
While Brnovich is running on his record, and is the only Republican in the primary who has won a statewide race, he has faced some blowback from Trump. Brnovich was one of the state officials who certified Biden's 10,457-vote .3% victory over Trump in 2020, and in May, Trump said that "Brnovich is nowhere to be found" while the "massive crime in the 2020 Election is becoming more and more evident and obvious." Brnovich has since spoken with Trump and defended the audit, telling the Justice Department that his office would "not tolerate any effort to undermine" it.
"Mark Brnovich is the clear choice for this time to ensure that the people of Arizona have a fighter in Washington, DC," said Brnovich spokesperson Joanna Duka. "The attorney general has a record of pushing back against the Biden Administration's disastrous border policy, fighting for election integrity, life, and defending the rule of law. He is on the front lines of the fights that matter most for hardworking Arizona taxpayers."
Masters and Lamon have sown more doubt about the results of the 2020 election even as they accept that Congress certified Biden's victory.
"Do I look back at what happened in November and see a really crazy, opaque, messy process that we shouldn't be making excuses for? Absolutely," Masters told CNN Tuesday. "I think it was messed up."
Lamon has donated millions of dollars to a voter registration group affiliated with prominent election fraud conspiracy theorists, according to Axios. He has taken to the airwaves in a bid for Trump's attention and possible endorsement, airing a TV ad on enhanced border security in New Jersey, where Trump is spending the summer at his Bedminster golf club.
Lamon told CNN in a statement that the election review would "help ensure that the American people have full confidence that all eligible Arizonans who cast ballots had their votes accurately counted." When asked who won the 2020 election, Lamon adviser Stephen Puetz wrote, "Congress has certified Joe Biden as the winner and he was sworn in. That's our process. ... AZ conducting an audit is part of the process as well."
Some Arizona Republicans worry that the state's election review and questions over the 2020 race will hurt whoever emerges to take on Kelly.
McGuire has attempted to separate himself from the others, touting himself as a non-self funder who never has served in elected office. But he also has been the only Republican Senate candidate willing to question the election review.
In an interview, McGuire told CNN that Biden was the "duly elected" president and said "there is no outcome that I see where there is a reversal" of the election because of the audit. He acknowledged that Trump did "very poorly" among women voters in the Phoenix and Tucson suburbs.
He allowed that not all Arizonans have confidence in the integrity of their elections but expressed ambivalence about whether Maricopa's audit will help or hurt the public's perception of the state's election integrity.
"I don't know if this audit will create greater confidence," he added.
The Republican candidates are running on similar platforms warning of price inflation, strengthening border security, and stopping the spread of critical race theory, which was an obscure academic framework for examining how racism is ingrained in American institutions until Trump declared it a villain last year. They all knock Kelly for saying he would be an independent, moderate voice, and link him to Biden and Senate Majority Leader Chuck Schumer.
That leaves the 2020 election and the candidates' personal background as the main points of contrast in the primary.
"The party apparatus is deeply entrenched in MAGA and it's the only litmus test that seems to matter at the moment," said an Arizona Republican operative.
Democrats hope that whoever emerges from the GOP field will be bruised by the primary. Kelly's fundraising machine is surging, raising $6 million in the second quarter of the year, and stockpiling nearly $7.6 million in a war chest. Republicans are far behind, although some can bank on outside Super PACs or the ability to fund their campaigns.
After about a month in the race, Brnovich raised about $438,000, while McGuire raised $226,500 and loaned his campaign another $200,000. Lamon raised $223,000 and loaned his campaign $2 million. Masters announced after the June filing deadline but can rely upon Thiel's largesse.
"The issues that we're facing in the state and across the country are significant," Kelly said. "This is a distraction."