Sen. Jeff Flake, center, campaigns in Arizona this week with a fellow Arizona Republican, Sen. John McCain, who faces a tough primary contest on Tuesday. (Paul Kane/The Washington Post)

TEMPE, Ariz. — Even when no one asks him about Donald Trump, Sen. Jeff Flake makes sure the audience knows how much he despises the Republican presidential nominee.

“No Trump questions,” the Arizona Republican mused at the end of two meetings on Tuesday with employees and executives at the Allstate Insurance office.

No matter.

Flake went on to tell the roughly 50 workers that he will not support Trump, “given the kind of campaign he is running.” He has “little faith” that Trump will change his ways, dooming him to defeat in November. Furthermore, Flake added, emphatically, “I don’t think he should win if he continues to campaign as he is.”

Sen. Jeff Flake (R-Ariz.) said Republican presidential nominee Donald Trump can't expect to win Arizona because he "needlessly" offends minorities. (Reuters)

Far from shading his views back home over Congress’s long summer recess, Flake is doubling down as one of the most outspoken critics of his party’s presidential nominee. He mocks as “a joke” the marquee idea behind Trump’s campaign, a wall along the Mexican border paid for by the Mexican government.

He’s now openly hopeful about Democratic nominee Hillary Clinton’s dealings with Congress if she defeats Trump, boasting about his close friendship with her running mate, Sen. Tim Kaine (D-Va.).

All of this has made Flake a massive political target for arch conservatives. The national spotlight will fall Tuesday on Sen. John McCain’s effort to beat back a tea-party-infused challenger in the state’s GOP primary. But here in Arizona there’s already talk about which conservative in 2018 will challenge Flake, the onetime conservative House firebrand with a libertarian bent whose image has shifted to the center in the Senate.

“Don’t get me started on Jeff,” former state senator Kelli Ward, McCain’s primary challenger, said in an interview at a Scottsdale campaign office. “I’ve been very disappointed in Jeff because he was sold to all of us as an extremely conservative man and politician and legislator, and he’s let us down on all fronts.”

Ward vowed to support a primary challenge to Flake even if she pulls off a stunning upset of McCain and eventually wins the Senate seat. “Hopefully there will be somebody good,” Ward said of a Flake challenge from the right. “If somebody good came up, I’d probably support them against Jeff.”

Not even Sen. Ted Cruz (R-Tex.), who has very strained relations with his colleagues, has ever openly supported a primary challenge to an incumbent Republican, let alone one from his own state.

Ward declined to state her own intentions about challenging Flake should she lose to McCain next week. But there’s already chatter that one of the more conservative members of Arizona’s congressional delegation would take on Flake, whose apostasies run from refusing to support Trump to aggressively supporting bipartisan immigration legislation to an overall demeanor of being nice to Democrats.

The list of Republicans who reject their presidential nominee, Donald Trump, and support his Democratic opponent keeps growing. (The Washington Post)

After Clinton selected Kaine as her vice-presidential nominee, Flake issued a mocking tweet toward conservatives about how he was trying to find something bad to say about the senator from Virginia. Instead, he congratulated Kaine as “a good man and a good friend.” He told reporters that he has “communicated” with Kaine since the nomination and believes he could be an emissary for bipartisan deals in the Capitol during a Clinton administration.

Kaine and Flake both joined the Senate in 2013 and have established a good working relationship as members of the Foreign Relations Committee on issues such as whether Congress should enact a new authorization for the use of military force to better define the fight against terrorism, including groups such as the Islamic State.

Flake has even abandoned the standard Republican line of repealing the Affordable Care Act. “This notion that we’re going to repeal it and replace it tomorrow, we could’ve never done that,” he said Tuesday at the Allstate event, noting that President Obama would always veto a bill that would end “Obamacare.” Assuming Clinton wins, the imperative for both sides is to work on smart fixes to the health-care system rather than uprooting the law, he said.

“You’ve got to work across the aisle, and I hope we can do it after this election,” Flake said. He dismissed the “Lock her up” chants at Trump rallies as part of “crazy conspiracy” theories toward the Clintons that serve only to poison the environment.

He’s well aware that his approach, particularly refusing to support Trump, could make winning a Republican primary more difficult in two years. “If I wanted to sail through reelection, this has made that tougher. No doubt,” he said in an interview after the sessions with Allstate workers. His campaign coffers are relatively low, having raised less than $400,000 in the first half of this year, which leaves him with $581,000 in his account.

Flake’s family name is literally synonymous with his home town, Snowflake, which his great-great-great-grandfather helped found as a Mormon settler. Flake ran the Goldwater Institute, named after Barry Goldwater, the state’s legendary conservative senator whose disastrous 1964 presidential campaign is drawing some comparisons to Trump’s this year.

Elected to the House in 2000, Flake was considered a strong conservative. His 2012 Senate bid was a competitive contest that he narrowly won, a race in which Hispanics accounted for about 16 percent of the vote. This year Hispanics might crest 20 percent of the vote in Arizona.

Flake has done the math about the changing composition of the electorate — including that younger voters are favoring Clinton by greater than 2-to-1 margins in some surveys — and he worries Republicans will “consign ourselves to political oblivion” without a dramatic shift in policy and tone. His main job this year has been to help McCain win reelection. At a rally at McCain campaign headquarters Tuesday, the 79-year-old incumbent praised his understudy for his “integrity” and called him “a man of honesty.”

Yet McCain has stood behind Trump, continuing to endorse the nominee even as he criticizes many of his proposals. Flake acknowledged that McCain might infuriate more Trump supporters than he’d win over in independents if he joined in rejecting Trump.

Then Flake reflected on how he would have handled things if it had been his turn this year to run for reelection, whether he would’ve been just as outspoken about Trump. What he said was the sort of answer that displayed an honest streak as well as a lack of political calculation.

“I would like to think so, but I can’t say,” Flake said. “To be honest, you know, I don’t know.”