The Republican Senate primary in Pennsylvania has featured months of aggressive  attacks between frontrunners Mehmet Oz and Dave McCormick — with an unexpected third candidate, Kathy Barnette, joining the mix of possible winners.

The Republican and Democratic primaries, which close on May 17, will determine the nominees to succeed retiring Republican Sen. Pat Toomey. Both parties are fiercely contesting Toomey’s seat, aiming to tilt control of the evenly divided U.S. Senate.

Oz, a newcomer to electoral politics but a surgeon widely known for his long-running TV show, secured the endorsement of former President Donald Trump. To get it, he beat out Dave McCormick, a former hedge fund CEO and onetime federal official under President George W. Bush, who has also sought to tie himself to Trump.

Ads for Oz blasted McCormick for his business ties to China and for alleged disloyalty to Trump. Ads for McCormick targeted Oz’s dual citizenship with Turkey, a line of attack that led Oz to say he would renounce his Turkish citizenship if he is elected. One super PAC opposing Oz aired an ad mocking the candidate for kissing his star on a Hollywood sidewalk; in a counter-ad, Oz called McCormick "part of the swamp that labeled President Trump as Hollywood."

Political analysts had always suggested that a third candidate could emerge as a serious contender if the attacks between Oz and McCormick soured voters on both candidates. In the race's closing days, that appeared to happen, as Barnette — another candidate who has aligned themselves with the Trump wing of the party — began rising in the polls, despite being outspent in television ads by a 358-to-1 margin.

A Fox News poll released less than a week before Election Day found Oz with the support of 22% of GOP primary voters, McCormick with 20%, and Barnette with 19%. That result echoed another poll from around the same period by the Trafalgar Group, a Republican pollster, which found Oz with 25%, Barnette at 23%, and McCormick at 22%. In the Trafalgar poll, all three candidates were within the margin of error. Polls from Monmouth University and Franklin & Marshall College produced similar results.

After Barnette’s fortunes began to rise, the conservative Club for Growth announced that it would be boosting her with $2 million for ads during the campaign’s final days. Her climb mirrored that of gubernatorial candidate Doug Mastriano, a state senator who sought to overturn Joe Biden’s victory in 2020 and went to the Capitol on Jan. 6, 2021, to protest the election results. Barnette and Mastriano have endorsed each other and campaigned together.

If Barnette were to win the nomination, it would scramble assumptions about Trump’s role in influencing the Republican base, since officially Trump is backing Oz.

The fireworks in the GOP primary have largely overshadowed the Democratic primary, which has produced a less divided field.

Lt. Gov. John Fetterman — a former mayor known for his burly, tattooed persona and his advocacy for legalizing marijuana — has consistently led the field of three main Democratic candidates. Fetterman faces U.S. Rep. Conor Lamb, a lawyer and Marine reservist, and state Rep. Malcolm Kenyatta, the first openly LGBTQ peson of color elected to the Pennsylvania legislature, and also one of the youngest.

Mehmet Oz: Campaign website  

Biography: Oz is a heart surgeon and attending physician at New York Presbyterian-Columbia Medical Center. He graduated from Harvard University and earned a joint MD and MBA from the University of Pennsylvania School of Medicine and Wharton Business School. Oz came to national prominence as a medical expert on Oprah Winfrey’s TV show, a role he later turned into his own syndicated program, "The Dr. Oz Show." He is also a New York Times bestselling author and has received a variety of patents for medical devices. However, other doctors have criticized Oz for endorsing questionable therapies on his show, such as diet and wellness supplements. Oz was born in Ohio to Turkish immigrants; he served in the Turkish military and said he kept his Turkish citizenship to ease visits to his ailing mother, who lives in Turkey. Oz is a longtime New Jersey resident who registered to vote in Pennsylvania in 2020 at his in-laws’ address.

Core policies: Oz is portraying himself as a political outsider, arguing that "feckless leadership in Congress means we have representatives who are more afraid of being ‘canceled’ and more interested in winning reelection than bravely challenging orthodoxy." Oz criticizes what he characterizes as groupthink in the response to COVID-19: "Dissenting opinions from leading scholars, even Nobel Laureates, were canceled and ridiculed so their ideas could not be disseminated. Doctors were forbidden from prescribing legal medications for the first time in our nation’s history." Oz now supports abortion restrictions, a change from past views.

Key backers: Trump, Fox News host Sean Hannity, rocker and conservative activist Ted Nugent, Rep. Guy Reschenthaler.

Dave McCormick: Campaign website

Biography: McCormick has deep pockets, thanks to his tenure as CEO of Bridgewater Associates, a hedge fund. He attended West Point, where he was a wrestler, and became an Army Ranger; he was one of the first U.S. troops to enter Iraq during the first Persian Gulf War and earned a Bronze Star. McCormick worked for international consulting firm McKinsey & Co. and later for FreeMarkets, a Pittsburgh-based technology firm. He earned a doctorate in international affairs from Princeton University and served in senior posts in the George W. Bush administration at the Commerce Department, the Treasury Department, and the White House. He is married to Dina Powell, who was President Donald Trump’s deputy national security adviser. McCormick was born in Pittsburgh and raised on his family’s farm in Bloomsburg, Pennsylvania, but he lived in Connecticut for more than a decade before running for Senate.

Core policies: Moving supply chains out of China and bringing manufacturing jobs back to the United States; encouraging coal mining and natural gas; toughening immigration enforcement, including building Trump’s border wall; opposing vaccine mandates; enacting voter ID requirements.

Key backers: National Border Patrol Council; Sen. Ted Cruz, R-Texas; former White House press secretary Sarah Huckabee Sanders; former Pennsylvania Senate candidate Sean Parnell. McCormick’s campaign has hired former Trump White House aides Stephen Miller and Hope Hicks.

Kathy Barnette: Campaign website

Background: Barnette, a former military reservist, has appeared on national TV and radio programs as a conservative, pro-Trump activist. She has said she is the "product of a rape." She lost a bid for the U.S. House in 2020.

Core policies: She wrote the book, "Nothing to Lose, Everything to Gain: Being Black and Conservative in America," which "explains why liberal policies have failed the Black community." At a debate, Barnette said it is "absolutely not" time for Republicans to move past the 2020 presidential election.

Key backers: Club for Growth; Former Trump National Security Advisor Michael Flynn; state Sen. and gubernatorial candidate Doug Mastriano; Rep. Burgess Owens, R-Utah; Pennsylvania State Police FOP Pioneer Lodge No. 37.

Jeff Bartos: Campaign website

Biography: Bartos owns a contracting company and several real estate acquisition and development companies in the Philadelphia metro area, and he has previously been a senior executive at Toll Brothers Inc. and Mark Group Inc. In 2018, Bartos was the GOP nominee for lieutenant governor after winning a four-way primary; the GOP ticket lost in the general election to Democrat Tom Wolf, who was running with Fetterman as his ticket-mate. Unlike McCormick and Oz, Bartos has been a Pennsylvania resident consistently in recent years, a difference he emphasizes on the campaign trail.

Core policies: While every GOP primary candidate running for Senate has courted the pro-Trump, strongly conservative base of the party, Bartos’ rhetoric is perceived as slightly softer. He has emphasized policies to curb opioid abuse and job creation. In response to the COVID-19 pandemic, Bartos founded the Pennsylvania 30 Day Fund, a nonprofit providing forgivable loans to small businesses affected by COVID-19.

Key backers: State Treasurer Stacy Garrity, some state lawmakers and municipal leaders.

Carla Sands: Campaign website

Biography: Sands was tapped by Trump to serve as U.S. Ambassador to Denmark, Greenland, and the Faroe Islands. Previously, she was a chiropractor and later chairman and CEO of Vintage Capital Group, a real estate company that her husband had led until his death in 2015.

Core policies: Sands’ agenda mirrors the other candidates, including criticism of the Democratic agenda and support for energy development. "We have enough under the ground right here in Pennsylvania to power our entire country for 300 years," she has said.

Key backers: Former House Speaker Newt Gingrich, plus several state legislators and Trump-era officials.

George Bochetto: Campaign website

Biography: A Philadelphia attorney, Bochetto received attention for defending a Christopher Columbus statue from being removed from a Philadelphia park. He has also been active in the case to keep Mumia Abu-Jamal, a man convicted of murdering a police officer in the 1980s, behind bars. Bochetto grew up in an orphanage in Brooklyn before being adopted. He earned his law degree from Temple University and ran unsuccessfully for Philadelphia mayor in 1999. He served as an appointed Pennsylvania State Boxing Commissioner from 1995 to 2002. Bochetto’s law firm aided Trump’s second impeachment defense.

Core policies: Bochetto has emphasized crime and justice. In a rally at police union headquarters, he was introduced by the widow of Daniel Faulkner, the Philadelphia police officer Abu-Jamal was convicted of killing.

Key backers: Former Pennsylvania Supreme Court Justice Sandra Schultz Newman; Fraternal Order of Police Philadelphia Lodge #5; Italian Sons and Daughters of Philadelphia

John Fetterman: Campaign website

Biography: Fetterman is the lieutenant governor of Pennsylvania, a position that also makes him chair of the Pennsylvania Board of Pardons. Previously, Fetterman served for 13 years as the mayor of Braddock, a low-income steel town near Pittsburgh. Fetterman got his start participating in AmeriCorps, the federal service program, in a lower-income neighborhood of Pittsburgh. He moved to Braddock to start a GED program and eventually ran for mayor in 2005. He has a master’s degree in public policy from Harvard University’s Kennedy School of Government.

Core policies: Fetterman, along with the other two Democratic candidates, supports raising the minimum wage to $15 an hour, abortion rights, voting rights, and an assault-weapons ban and expanded gun background checks.

Fetterman’s signature issue is marijuana legalization, taking the idea on the road by holding meetings in all 67 counties in the state. Related to his position on marijuana, Fetterman has advocated for criminal justice reform, including in his role on the pardons board. Fetterman touts having taken "numerous steps to overhaul the clemency process in Pennsylvania, including eliminating all fees associated with applying for a pardon, making the pardons application more user-friendly, and working to move the application process online."

Fetterman has also been supportive of LBGTQ rights, officiating one of the first same-sex marriages in the commonwealth. As mayor, he worked to block a four-lane Interstate highway from going through Braddock, arguing that the 80% Black community "already suffered historically high asthma rates."

Key backers: United Steelworkers, UFCW 1776, National Organization for the Reform of Marijuana Laws, various local Democratic officials.

Conor Lamb: Campaign website

Biography: Lamb is a Marine and a former federal prosecutor who is currently representing a district north of Pittsburgh in the U.S. House. Lamb initially won his seat in a special election in March 2018, running in a district to the south that Trump had won by nearly 20 points. Lamb went on to win re-election in a different district in November 2018 and 2020.

Core policies: Lamb has run for the House as a moderate, though he’s shifted to the left somewhat while running in the current Senate primary. Perhaps his biggest break with Democratic orthodoxy has been his opposition to a ban of fracking, a method of natural gas extraction that has been a major economic engine in southwestern Pennsylvania. "We need to be honest about the fact that natural gas is a critical bridge fuel that helps us keep people warm and keep the lights on at a price people can afford, and it is American-made," Lamb said on his website.

Lamb has also said that he personally opposes abortion but has voted in line with pro-abortion groups such as Planned Parenthood since serving in Congress.

Key backers: Building trade unions, the National Organization of Women, many state and local Democratic elected officials.

Malcolm Kenyatta: Campaign website

Biography: The race’s youngest candidate at 31, Kenyatta is Black and openly gay. He represents a Philadelphia-based district in the state House and is a member of the governor’s Suicide Prevention Task Force. He was part of a keynote address of "rising stars" at the 2020 Democratic National Convention.

Core policies: Kenyatta’s positions are largely in line with those of his primary rivals. The biggest difference is on fracking policy; he has taken the strongest line of the three against fracking, urging a moratorium on new drilling sites. Like Fetterman, he supports federal legalization of marijuana.

Key backers: The American Federation of Teachers, some Democrats in the legislature, and some unions.

Dave McCormick: "We all know China created COVID." (False)

Mehmet Oz, "David McCormick fired Pennsylvanians and bragged about shipping their jobs to Asia." (Mostly False)

Mehmet Oz, "David McCormick paid for attacks on Donald Trump." (False)

Carla Sands, "Joe Biden's "$4 trillion" Build Back Better bill is "the largest expansion of welfare programs in 60 years." (Half True)

Penn Progress, a Pro-Conor Lamb super PAC: "John Fetterman's a self-described democratic socialist" (False)

Dave McCormick: "Mehmet Oz 'called for a New Zealand-style gun ban" and said "Americans should have less access to guns.'" (Mostly True)

Mehmet Oz, "Dave McCormick is "liberal, pro-Biden, pro-China." (False)

Pennsylvania Conservative Fund, "Mehmet Oz ‘was a spokesman for a group who wanted to defund the police.’" (False)

"Fact-checking a super PAC attack on Dr. Oz over defunding police, Obamacare, COVID-19, immigration"

Dave McCormick, "Mehmet Oz is ‘pro-abortion’" (Mostly False)

Kathy Barnette: Joe Biden "inherited inflation of 1.7%. Now we're well over 8% and growing." (Mostly True)

Kathy Barnette: "Agriculture is the No. 1 industry here in Pennsylvania." (False)

USA Freedom Fund: "Kathy Barnette wants to build a statue of Barack Obama right next to the one of Abraham Lincoln on Capitol Hill." (Mostly True)

CORRECTION, May 13, 2022: This article has been updated to remove outdated information about Sands being the only top-tier woman in the race. According to polls, Barnette is now a significant contender.