Rep. Martha McSally appears poised to challenge Kelli Ward in what would be a vicious primary fight for Jeff Flake’s Senate seat, but President Donald Trump remains a major wild card.

Rep. Martha McSally is taking steps toward launching a challenge to Kelli Ward for Sen. Jeff Flake's seat next year, a move that would set up another scorched-earth primary battle between establishment Republicans and former White House chief strategist Steve Bannon.

The second-term congresswoman indicated her interest in the seat during a closed-door meeting Thursday with Arizona's five-member GOP House delegation, and also met Thursday with Sen. John McCain to consult about a statewide contest, an Arizona Republican with knowledge of the situation says. Even before that, she began polling her prospects.

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"She wants to lay down a marker immediately," the Arizona source says. "She hates the House."

Not long after Flake's retirement announcement Tuesday, White House officials began reaching out to Arizona's GOP lawmakers to field interest in the seat, two separate sources tell U.S. News – a clear indication of their aversion to Ward.

Reps. Trent Franks and Paul Gosar, two conservative House members, have publicly ruled out bids, although Gosar reportedly still expressed interest in a run during Thursday's delegation meeting. And Rep. David Schweikert, a four-term congressman and member of the House Freedom Caucus like Franks and Gosar, quickly declined the overture.

"The office he's most interested in running for is governor in 2022," Schweikert spokesman Kevin Knight says.

The two GOP sources say the winnowing field makes McSally, a retired U.S. Air Force colonel first elected in 2014, the front-runner to become the consensus candidate of lawmakers and donors. While McSally has not yet made a decision, one congressional aide says based on the congresswoman's initial conversations with colleagues this week, she's expected to run.

"The biggest dilemma is handing her seat off to Ann Kirkpatrick," says the aide, referring to the former Democratic congresswoman running to claim the seat in McSally's swing district. "But the federal delegation will get behind Martha."

McSally's office did not respond to questions.

On Friday, Jeff Roe, McSally's chief consultant, denied the campaign was conducting any polling on the race.

"No, we're not polling. And she doesn't need a poll to tell her whether she wants to run or not," Roe tells U.S. News. "I have no idea what she's going to do. She doesn't know what she's going to do. She doesn't need to talk to donors and do a poll to decide what she wants to do. She has to pray about it, think about it, understand the contours of the potential campaign."

But if McSally pulls the trigger on a campaign against Ward, it could set off another civil war reminiscent of the GOP Senate runoff in Alabama, in which Roy Moore defeated Sen. Luther Strange.

The looming question is: On which side would President Donald Trump fall?

Just last week, Bannon, the executive chairman of Breitbart News who's attempting to launch a party insurrection in the 2018 midterms, traveled to the Grand Canyon State to endorse Ward. Bannon described her as a "whirlwind" that would be unleashed against Senate Majority Leader Mitch McConnell and the "new aristocracy" of Republican congressional leadership.

But while Ward has presented herself as an avatar of Trumpism, many Republicans view her as a fringe figure prone to making comments out of the mainstream, and fear a Ward nomination would hand the seat to Democratic Rep. Kyrsten Sinema, who announced her Senate run last month. This is why White House advisers have cautioned the president against a full-throated endorsement of Ward, leaving her twisting in the wind even as she was thumping Flake by double digits in primary polling.

McSally, though, could be an anathema to the Trump movement, and potentially to Trump himself.

She declined to publicly endorse Trump during the 2016 campaign, and disagreed with his rhetoric on how the U.S. might abandon its NATO allies if they didn't fulfill their financial obligations. She also voiced concerns about how "he's spoken about veterans and Hispanics and women and others."

"That's just not how leaders carry themselves," she said in July of 2016. After the infamous "Access Hollywood" tape detonated, she dubbed Trump's comments "disgusting" and "unacceptable," but remained inscrutable about supporting him.

For Bannonites, a McSally candidacy would provoke a full-fledged intraparty war.

"If the McConnell establishment runs another 'Never Trumper' in Arizona like Martha McSally, expect the full weight of the president's America First movement to come down upon her like a ton of bricks," says Andy Surabian, an adviser to Trump-aligned advocacy organization the Great America Alliance and a close Bannon adviser.

An Arizona GOP operative familiar with the potential fleet of candidates in the race also described a McSally candidacy as problematic.

"McSally's place in the race does nothing to scare off Ward or Bannon," he says. "Someone just left the stage that at the end of the day was not part of the Trump Republican Party. McSally's not part of that contingent, either. No one's going to confuse her for a conservative."

McSally's advocates argue the congresswoman is a proven fundraiser and disciplined messenger who can unite moderates and conservatives and ultimately would match up better with Sinema, a candidate who is likely to avoid a bruising primary and become what one conservative lobbyist in Arizona describes as "the most formidable Democratic Senate opponent in 30 years."

The congressional aide familiar with the delegation's dealings says the White House officials, during their outreach, were not trying to persuade someone who wasn't interested in a campaign, and made no ironclad promises about an endorsement.

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Such a vow could prove dangerous with an impulsive president like Trump. It's unclear if he even knows McSally never pledged support to him, and it's unknown how he would personally react to such news.

In May remarks at the White House, Trump referred to McSally as "my friend" and the "real deal," and the congresswoman has regularly aligned with Trump in her congressional votes. Still, the president isn't known for showing restraint in looking past prior criticisms.

Ward, meanwhile, is racing to position herself as the front-runner for the seat, blitzing national television and radio programs in the wake of Flake's announcement.

In rolling out the appointment of longtime GOP consultant Ed Rollins as her campaign chairman Wednesday, Ward sought to inject mainstream credibility into her endeavor. Rollins managed President Ronald Reagan's 1984 re-election campaign and helmed Mike Huckabee's 2008 White House run.

"She's well in tune with this Trump coalition agenda that really the establishment doesn't understand. We feel we're in pole position in this race. Her name ID is in the 80s," says Eric Beach, a top strategist for Ward's campaign. "We're going to have the necessary resources to start a contrast with Sinema."

Almost everyone agrees that Ward will have a tough primary first – but figuring out the best candidate to match up against her continues to be a point of discussion. State Treasurer Jeff DeWit is said to be still weighing the race, even though he has been reluctant to move ahead with a campaign for months and seems content in Phoenix. Former Arizona Gov. Jan Brewer is said to be pushing Jay Heiler, a member of the state's Board of Regents with little known constituency. And former Rep. Matt Salmon is fielding calls, processing what a race would entail, an adviser says.

Playing into the puzzle is the unspoken calculation that Sen. John McCain's seat will become open before his term is up, due to his deteriorating health. McCain is battling an aggressive form of brain cancer and has said his prognosis is "very poor." If he were to leave office, Gov. Doug Ducey, a Republican, would be tasked with naming his replacement. In fact, the Arizona Republican source says McSally huddled with her strategists last week – days before Flake's announced departure – to discuss the ramifications of McCain's departure.

The prospect of a combative, bloody primary must be weighing on McSally. A fight with the president might be too much to bear.

Establishment forces believe Ward can't be the nominee. They're now struggling with whether they can agree on who should be.

But asked about the prospect of the GOP establishment fielding opponents against her, Ward remained defiant to Sean Hannity: "They were wrong in Alabama. And they're going to be wrong again in Arizona."