(Bloomberg) -- Pennsylvania is at the heart of a dramatic midterm primary election race. On the Republican side there is a former Wall Street executive vying with a celebrity physician and a surging conservative firebrand. Their likely rival is a Democrat recovering from a stroke.

For months, the GOP race for an open US Senate seat was between Mehmet Oz, known as “Dr. Oz,” and former Bridgewater Associates Chief Executive David McCormick, who with their allies had spent more than $54 million on ads -- a record for a Senate primary in the commonwealth. But commentator Kathy Barnette roiled the campaign with a late surge to make it a statistical tie in two polls released days before the primary.

The winner of Tuesday’s primary will likely face John Fetterman, the Keystone State’s Democratic gym shorts-wearing lieutenant governor, who announced on Sunday he was hospitalized for a stroke but was “well on my way to a full recovery.” He holds a commanding lead in polls over his nearest rival, US Representative Conor Lamb. 

The Republican race is also another test of former President Donald Trump’s grip on the GOP and whether his base voters follow his endorsements as he seeks to elect loyal candidates and teases another White House bid in 2024.

Earlier this month, Trump scored a victory in neighboring Ohio when his endorsement helped “Hillbilly Elegy” author JD Vance come from behind to win the Republican primary for an open US Senate seat. But Trump’s imprimatur hasn’t given Oz the same boost, and he’s struggled to separate from McCormick and a rising Barnette.

Last week, as polls showed Barnette rapidly ascending, Trump did a “tele-town hall” with Oz and issued a statement arguing Barnette couldn’t win the general election. That followed a May 6 Pennsylvania rally for Oz, where the former president tore into McCormick as “a liberal Wall Street Republican.”

While Republicans are favored to take the US House in this year’s midterm elections, Democrats have eyed the Pennsylvania seat of retiring Republican US Senator Pat Toomey as a potential pickup to maintain control of the upper chamber. Democratic candidates face headwinds in the form of rampant inflation and President Joe Biden’s low approval ratings. 

Abortion has roared to the fore with the leaked US Supreme Court draft opinion that would overturn Roe v. Wade. In Pennsylvania’s GOP Senate race, Barnette has emphasized her story of being the product of a rape when her mother was 11.

Barnette has also aligned with state Senator Doug Mastriano, the leading Republican candidate in the crowded race for the commonwealth’s open governor’s seat and a prominent supporter of Trump’s false 2020 election claims. Barnette organized buses to the “Stop the Steal” rally on Jan. 6, 2021, that preceded the attack on the U.S. Capitol.

Trump endorsed Mastriano on Saturday even as some Pennsylvania Republican leaders expressed concern that Mastriano could lose a general election to likely Democratic nominee Josh Shapiro. They have staged a late effort to coalesce behind former US Representative Lou Barletta.

Barnette’s rivals also argue she would struggle in a general election because of her previous homophobic and anti-Muslim comments, as well as her largely unvetted background. 

Oz said in an interview after a campaign stop in suburban Philadelphia on Saturday that Barnette’s comments disqualify her from serving and that Republicans would lose the seat if she were nominated in part “because she’s an unknown.” 

Barnette responded during a stop at a car show in Philadelphia on Sunday that most of the comments are old, “half-thoughts” taken out of context, and that she finds Oz’s ties to Turkey disqualifying. Oz has said he’ll renounce his Turkish citizenship if elected.

McCormick hasn’t focused on Barnette but has called Oz a “Hollywood liberal” and cited comments on his “Dr. Oz Show” and other forums to accuse him of flip-flopping on issues including abortion, fracking and gun control. 

“His positions that he said in his own words over 20 years don’t line up with Pennsylvanians,” McCormick said in a May 6 interview. A West Point graduate who served in the Gulf War and was a US Treasury undersecretary for international affairs under George W. Bush, McCormick’s campaign mantra was that he is “battle-tested,” and that he will be “someone who will be a conservative leader in the Senate.”

McCormick was endorsed by US Senator Ted Cruz of Texas, who campaigned with him in the final days of the race, as well as former Secretary of State Mike Pompeo.

Oz said the endorsements from Trump and other leading Republicans prove his conservative bonafides. He said he can best appeal to suburban women and voters who will decide a general election because they know him from his long-running TV show.

“I’m positioned to win it because for 13 years, I’ve been in everyone’s living room, everyone’s bedroom, talking to them about things that matter to them,” Oz said in the interview on Saturday.

Oz and his allies have hammered McCormick for his ties to China -- a major issue with working-class voters unhappy about outsourced jobs and the coronavirus pandemic -- especially Bridgewater’s billion-dollar fund there. 

Analysts said Barnette, who ran a tenacious campaign despite spending less than $2 million -- including only $199,000 on ads, according to AdImpact -- received a look from many undecided voters as McCormick and Oz discredited each other. She was helped in the last week with a $2 million ad buy from Club For Growth Action and an endorsement from the anti-abortion Susan B. Anthony List. 

Barnette, who would be the first Black GOP woman elected to the US Senate should she win the primary and general elections, said her campaign gained momentum after Trump’s April 9 endorsement of Oz. 

“People began to actively get off the sidelines and start looking for a conservative,” Barnette said in a May 12 telephone interview. “Having a warm body with an ‘R’ next to their name, but don’t share our values, that’s not enough for people.”

Other candidates in the seven-person GOP field include real estate developer Jeff Bartos and Carla Sands, Trump’s former ambassador to Denmark, but they never gained traction.

There are also primaries on Tuesday in four other states, including for the US Senate in North Carolina, where Trump’s endorsed candidate, Representative Ted Budd, is leading former Governor Pat McCrory in polls. The state’s party leadership has also opposed US Representative Madison Cawthorn’s re-election bid.

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