Sen. Jeff Flake (R-Ariz.) says the Republican president in the White House is not displaying the conservatism his party should be embracing. In his new book, "Conscience of a Conservative," Flake says populism and protectionism are as threatening to the GOP now as the New Deal was in 1960. (Dalton Bennett,Kate Woodsome/The Washington Post)

Sen. Jeff Flake (R-Ariz.) says the Republican president in the White House is not displaying the conservatism his party should be embracing. In his new book, "Conscience of a Conservative," Flake says populism and protectionism are as threatening to the GOP now as the New Deal was in 1960. (Dalton Bennett,Kate Woodsome/The Washington Post)

Long-shot Senate candidate Kelli Ward was sound asleep just after 4 a.m. in Arizona last week when President Trump praised her on Twitter. She and many other Republicans were caught by surprise — and her phone started buzzing immediately.

“It hasn’t stopped since,” Ward said.

Neither has the controversy that erupted within the Republican Party after Trump inserted himself into the primary contest between the little-known former state legislator and one of the president’s most vocal GOP critics: Sen. Jeff Flake (Ariz.).

As Trump prepares for a rally in Phoenix on Tuesday, some expect him to expand on his support for Ward and searing criticism of Flake — and perhaps even make a formal endorsement.

That possibility has unnerved Republicans inside and outside the White House. Some worry about straining the president’s already tenuous relations with congressional Republicans at a time when they face several key challenges this fall: raising the debt ceiling, passing a spending bill and tackling their top policy objective of new tax legislation. Others looking ahead to next year’s midterm elections think Trump may even be putting the Senate GOP majority at risk.

Sen. Jeff Flake, R-Ariz. walks to his seat as he attends a luncheon with other GOP Senators and President Donald Trump at the White House in Washington on July 19. (Pablo Martinez Monsivais/AP)

Allies of Flake, including Senate Majority Leader Mitch McConnell (R-Ky.), are vexed by Trump’s posture. At a minimum, they think he is needlessly creating a costly primary that will suck resources away from other targets on a map ripe for gains.

“There are 10 Senate Democrats up for reelection in states the President won in 2016, and that’s where his political focus and energy ought to be over the next 14 months, instead of harmful intraparty warfare,” said Brian Walsh, a former communications director for the National Republican Senatorial Committee.

Indeed, just last week the Cook Political Report downgraded the chances for four incumbent Democrats from states Trump won last year, giving the president a clear road map, according to many Republicans, to help protect and even expand the GOP majority. Instead, he is targeting an incumbent in his own party who has not been shy about criticizing him — and seemingly bolstering a challenger who lost resoundingly last year to Sen. John McCain (R) and whose bona fides have raised concerns even inside the White House.

Last Thursday, Trump tweeted that it was “Great” to see Ward running against Flake, whom he disparaged as “WEAK on borders, crime and a non-factor in Senate.”

Yet in the lead-up to the tweet, White House aides explored the possibility of trying to draw others into the race who might pose a stronger challenge to the senator — and pursued opposition research on Ward, said Republicans familiar with the situation who spoke on the condition of anonymity to be candid.

[Is President Trump trying to beat Republican Jeff Flake next year? Flake doesn’t care.]

The White House press office did not immediately respond to a request for comment.

Ward, meanwhile, is eager to tether herself to Trump.

“This is definitely a nationalized race,” she said in an interview. “I know that people in Arizona can only vote for me, but there are people all across the country who know that when I get into the Senate, I’ll be voting for Trump.”

An official Trump endorsement would be a serious breach of GOP decorum that calls for Republicans to stand by fellow incumbents. Some Republicans said privately that they would be surprised if the two made a joint appearance during Trump’s trip to Phoenix. But several, including McConnell, have defended Flake publicly since Trump’s tweet.

“Arizonans are well-served by the principled leadership of @JeffFlake,” Senate Majority Whip John Cornyn (Tex.) tweeted Monday. “He always fights for what’s best for #AZ & we need him in the #Senate.”

Ward would say only: “I’m at the mercy of the powers that be. We’ll see.”

Flake is not planning to attend Trump’s rally. An aide, who spoke on the condition of anonymity to be frank, said a Trump endorsement of Ward would be “a massive turning point in the race without a doubt.”

Flake brushed off the coming challenge in an interview earlier this month. He faced a competitive 2012 primary and general-election campaign, he said, and he expects the same next year. “We knew from the beginning that we’d have a tough primary, we’d have a tough general,” he said.

[Deepening GOP split, Trump attacks Republican senators Graham, Flake as ‘publicity-seeking,’ ‘toxic’]

Most of Flake’s thoughts about the political climate are conveyed in his recent book, “Conscience of a Conservative: A Rejection of Destructive Politics and a Return to Principle,” a national bestseller that he wrote without informing his closest advisers and allies until just before its publication. The book details Flake’s specific concerns about Trump’s tone and temperament, as well as his approach to U.S. foreign policy, immigration, taxes and trade.

On Monday, Ward’s campaign released a digital ad that targets voters in the Phoenix area and questions Flake’s GOP credentials. “Senator Flake, why are you still attacking the president?” an announcer asks. “Just to sell copies of your new book?”

Some of Flake’s detractors in Arizona consider the book part of his exit strategy. “I think there’s a part of him that almost assumes he’s going to lose and he’s going to go out in a blaze of glory. Otherwise, this book doesn’t make much sense,” said Constantin Querard, a conservative Republican campaign consultant based in Phoenix who doesn’t support the senator.

But Ryan O’Daniel, another Phoenix-based GOP operative, said the book is “Jeff being Jeff.” He added: “I don’t think there are very many Republicans that disagree with the principles that Flake is espousing and talking about.”

Ward, 48, is an osteopath and a former state senator who unsuccessfully tried to use McCain’s age against him. She earned just under 40 percent of the vote — and announced her campaign against Flake in November.

Ward has a history of making controversial statements. In an interview with The Washington Post earlier this month, she suggested that Flake doesn’t have a brain or a backbone. And she mailed potential donors an envelope this month with an image of comedian Kathy Griffin holding what appeared to be the severed head of Trump. “It’s important to see what we’re up against,” she said in an enclosed letter.

For Trump, there is a personal risk in supporting a candidate as unpredictable as Ward. If she loses, it would send a message to the rest of the party that he is unable deliver on his threats of retribution.

For others, his support for Ward could complicate efforts to retain and even build the GOP Senate majority — a top priority to make it easier to pass the big-ticket items they have struggled to spearhead this year, including the failed overhaul of the nation’s health-care system.

In private, some have contemplated a devastating scenario in which they don’t pick up any Democratic seats and lose their majority. In that outcome, their most vulnerable incumbent, Sen. Dean Heller (Nev.), would lose, Democrats would win Flake’s seat, and McCain, 80, who has brain cancer, would leave his seat and trigger a special election that Democrats would win.

In Arizona, Ward has grown her campaign considerably in the past few weeks, hiring Eric Beach, a founder and director of the Great America PAC, which spent about $30 million backing Trump’s campaign in 2016, and other aides.

Flake has national allies gearing up to bolster him through what could be a bruising primary. The NRSC, the GOP’s Senate campaign arm, and the Senate Leadership Fund, a group headed by former aides to McConnell, are in Flake’s corner, keeping with the groups’ tradition of supporting incumbents.

The Club for Growth, a conservative advocacy group that supported Flake when he first ran for the Senate in 2012 and which has clashed with Trump, is also defending him, even though it has not officially endorsed him.

Flake’s backers have signaled that they intend to cast Ward as a fringe challenger. McCain branded her “Chemtrail Kelli” during her run against him, as part of an effort to tether her to a conspiracy theory about airplanes spreading chemicals. Ward has discussed the theory and used her perch as a state lawmaker to investigate it, but she has said she does not believe it.

The GOP primary is still more than a year away. Flake has not started actively campaigning for reelection. On Monday, he appeared at a Chamber of Commerce breakfast in Gilbert, Ariz., before holding a Facebook Live event on veterans and small-business issues.

In addition to starting earlier, Ward is once again helped by the independent Kelli PAC, which supported her 2016 bid. The PAC received a $300,000 donation this month from Robert Mercer, a billionaire Trump supporter who has bankrolled other conservative efforts. Mercer made a similar donation in 2016.

Democratic groups are also watching the contest and weighing whether to spend money quietly boosting Ward through the primary to produce a weaker general-election opponent. Several Democrats are considering running, including Rep. Kyrsten Sinema, a centrist who said she is “seriously considering” the race. Sinema has voted against House Minority Leader Nancy Pelosi (D-Calif.) for speaker and who is the first openly bisexual person to be elected to Congress.

“We’re interested in winning. And we do what we need to in order to win,” said J.B. Poersch, president of the Democratic-aligned Senate Majority PAC, in an interview with The Post and McClatchy News that aired over the weekend on C-SPAN’s “Newsmakers.”

Although many see a complex web of variables that could leave marks on the political landscape well beyond Arizona, the choice to go after Flake was simple for Trump. As he said on Twitter last week, “He’s toxic!”

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