SCOTTSDALE, Ariz. — Rep. Martha McSally of Arizona sees her race for the Senate as a make-or-break one for Republicans.

“They know if there’s any chance to flip the majority, it goes through Arizona,” the two-term congresswoman said of the Democrats while addressing a friendly audience here at a synagogue Wednesday night. “I’m literally a firewall to make sure that Chuck Schumer and his allies are not in charge.”

Other Republicans in red states that President Donald Trump won handily two years ago are nationalizing their races, arguing that GOP control is necessary to maintain a strong economy and support the president’s agenda.

[Sinema Hews to the Middle in a Changing Arizona. Will It Be Enough to Win?]

McSally is testing whether or not the same strategy will work in her race against Democratic Rep. Kyrsten Sinema in a state that could be trending purple — Trump carried Arizona by just 4 points. Republicans are confident it will.

“It’s Martha’s [race] to lose right now,” said Robert Graham, the former Arizona GOP chairman.

What to Watch in the Final Stretch of the Arizona Senate Race

Right moves

Either McSally or Sinema would be the first female senator elected from Arizona. Being a trailblazer isn’t new for McSally — before her election in 2014 to her Tucson-area district, she served more than two decades in the Air Force and was the first female fighter pilot to fly in combat.

In the House, she largely cultivated a more moderate profile. (Her 2nd District backed Hillary Clinton two years ago.) But that reputation came under fire during a lengthy and divisive Republican Senate primary this year.

Her opponents — former state Sen. Kellie Ward and controversial former Maricopa County Sheriff Joe Arpaio — argued she wasn’t a strong Trump ally, citing her criticism of him in 2016 for his disparaging comments about women.

McSally has since embraced the president and emerged victorious from the late-August primary with 53 percent of the vote. Trump’s recent visit to the state likely helped in her efforts to unite the party around her candidacy, said Chuck Coughlin, an Arizona GOP consultant. 

Her focus on the election’s partisan stakes is resonating with some Republicans, like Jim Bloch, a 73-year-old Scottsdale resident who attended Wednesday’s event at Congregation Beth Tefillah.

“I wouldn’t vote for a Democrat if my life depended on it,” said Bloch, a self-described conservative, not registered with any party. He attributed his stance largely to the intense confirmation fight over new Supreme Court Justice Brett M. Kavanaugh, who faced allegations of sexual assault, which he strongly denied. 

Republicans have been hopeful that the court battle could boost energy among GOP voters in a race that Inside Elections with Nathan L. Gonzales rates a Toss-up. Recent polls are already pointing to the race trending in McSally’s favor, which some credit to GOP voters waking up.

“This could be a ‘Put your jerseys on’-type moment,” one Republican strategist involved in Senate races said.

And there are more signs for GOP optimism in the early ballot count — Republicans have been outpacing Democrats so far in a state where the vast majority of votes are cast before Election Day.

“That [Democratic] wave that we were anticipating, we’re not seeing,” Coughlin said of the initial returns. “It’s a typical midterm cycle that we’re looking at.”

Bloch has already cast an early ballot for McSally.

“It’s a party vote more than anything else. I like what this woman stands for, but it’s a party vote,” he said. 

The “party vote” could give McSally an advantage in a state where a plurality of voters, 35 percent, are registered Republican. Thirty-three percent are not registered with a party, and 31 percent are registered Democrats.

And then there’s Sinema, whom some Republicans credit for helping to bring in GOP voters skeptical of McSally’s conservative credentials. While the Democrat has stressed her moderate record in Congress, her past as a liberal state legislator and anti-Iraq War activist has been the subject of countless GOP attacks. 

“Even if people don’t like McSally, for one reason or another, they’re voting for her,” said Graham, the former state party chairman. “They will never, never, never vote for Kyrsten Sinema.”

Swing voters

Conservatives may be energized to vote against Sinema, but Democrats argue their candidate is winning over Republicans. McSally hinted as much Wednesday night.

“I need you to talk to your friends because a lot of them think she’s OK. … But she’s not,” McSally told the crowd at the synagogue.

She said on a local radio show earlier this month, “We’ve got some moderate Republicans who seem to have drank Kyrsten Sinema’s Kool-Aid in the polling, and we need to bring them back home.”

Sinema has acknowledged her shift to the center since being elected to the House. She was able to communicate with voters early, with TV ads that stressed her independent streak. And she went uncontested on the airwaves while the Republicans fought among themselves in the primary. 

“Looking back on it, an outside group should have been up going after her while the primary was going on,” one GOP strategist said.

Asked Wednesday if she was still concerned about moderate GOP voters backing Sinema, McSally said, “Look, with millions of dollars of the reinvention of who she is to something that she’s not. She’s fooled people for sure.”

Watch: McSally Defends Health Care Record in Testy Media Exchange

Health care has emerged as a top issue in the race, with Democrats hopeful — and some Republicans concerned — it could cost McSally support among nonpartisan voters as well as GOP women. 

Sinema has knocked McSally for her vote last year for the GOP plan to mostly repeal the 2010 health care law. Sinema has said the bill would strip protections for people with pre-existing conditions, while McSally has cast her vote as one that would have protected those people.

(The GOP bill technically barred insurance companies from refusing to cover people with pre-existing conditions, but allowed for states to waive regulations, which could have rendered health care for those people unaffordable.)

Health care was certainly at the top of Dee Dee Nadler’s mind when she came to the synagogue here Wednesday night. During a Q&A session, the registered Republican and undecided voter asked McSally about her position on health care and Medicare. 

McSally stressed her support for protecting Medicare and people with pre-existing conditions, but said the health care law was not sufficiently providing coverage and also raising health care costs.

Nadler, who is older but declined to give her age, said she liked what McSally had to say. She was also drawn to the candidate’s military background, but she still wanted to do more research on both candidates. 

“Am I leaning towards her?” Nadler said. “More than I was [before].”