The G.O.P. Senate primary in Pennsylvania remains a tossup as an election denier wins the Republican primary for governor.

Doug Mastriano, a far-right Republican state senator who marched on the Capitol on Jan. 6, 2021, and emerged as a leading denier of the 2020 election results, won his party’s nomination for governor of Pennsylvania on Tuesday, as the battleground state’s hotly contested Senate Republican primary remained too close to call.

The rise of Mr. Mastriano, the Republican front-runner even before a bandwagon-boarding endorsement by Donald J. Trump over the weekend, had the old guard of his party scrambling to derail him and pointing fingers as that became impossible, fearing that the conspiracy-promoting legislator would prove too extreme to win this fall.

“God is good, all the time,” Mr. Mastriano said in his victory speech, outlining “day one” goals that included “mandates are gone,” “any jab for job requirements are gone,” critical race theory is “over,” “only biological females can play on biological female teams” and “you can only use the bathroom that your biological anatomy says.”

The Republican Governors Association issued a tepid response after the race was called, not promising financial support. “The RGA remains committed to engaging in competitive gubernatorial contests,” the group’s executive director, Dave Rexrode, said in a statement.

In the Senate race, the celebrity physician Dr. Mehmet Oz and David McCormick, the former chief executive of the world’s largest hedge fund, had bludgeoned each other on the airwaves and on the campaign trail for months in the Republican primary. With more than 90 percent of the vote counted, they were knotted together — and possibly within range of a recount, which is triggered under state law if the margin is 0.5 percent or less of the total vote.

Both Mr. McCormick and Dr. Oz said in speeches to supporters that there would be no immediate result.

“We have tens of thousands of mail-in ballots that have not been counted,” Mr. McCormick told the crowd at his election night watch party in Pittsburgh late Tuesday night, leaving unsaid that top Republicans have systematically sought to undermine faith in such ballots since 2020.

Kathy Barnette, a far-right commentator who has a history of expressing homophobic and anti-Muslim views, made a surprising late surge on the strength of her compelling personal story but was farther behind.

In a sign of the race’s importance this fall, President Biden congratulated the Democratic nominee, Lt. Gov. John Fetterman, and said of the G.O.P. field that “whoever emerges will be too dangerous, too craven, and too extreme.”

Mr. Mastriano’s victory sets up a fall clash with Attorney General Josh Shapiro, who was unopposed in the Democratic primary, a matchup with vast potential consequences both for state-level issues like abortion rights and for election certification in the 2024 presidential race.

Pennsylvania Republicans who fully control the Legislature are likely to attempt to restrict abortion rights if the Supreme Court overturns Roe v. Wade, as expected. That means whoever occupies the governor’s residence in Harrisburg would determine whether such a bill becomes law. And the Pennsylvania governor appoints the secretary of state, whose office will oversee the 2024 election.

Mr. Mastriano and Ms. Barnette formed something of a hard-right ticket, endorsing one another as they attempted to fend off their better-funded rivals. Dr. Oz relied heavily on the conservative credibility he gained from Mr. Trump’s endorsement while Mr. McCormick’s Wall Street allies flooded the airwaves with attack ads.

Five states — Pennsylvania, North Carolina, Kentucky, Oregon and Idaho — held primaries on Tuesday, with the outcomes signaling the relative strength of the ideological factions in both political parties.

In North Carolina, Representative Madison Cawthorn, a Trump-backed Republican who has created a string of controversies and mini-scandals, including his comment that some colleagues in Washington had indulged in cocaine and orgies, conceded defeat to his primary challenger on Tuesday night, State Senator Chuck Edwards. He became the first incumbent who was not facing another member of Congress to lose a primary in 2022.

Also in North Carolina, Representative Ted Budd handily won the Republican nomination for an open Senate seat, riding an early Trump endorsement and millions of dollars in outside spending to best former Gov. Pat McCrory, in another sign of the diminished standing of the party establishment. Mr. Budd will face Cheri Beasley, a Democrat who is a former chief justice of the State Supreme Court and who would become North Carolina’s first Black senator if elected.

In Idaho, another Trump-backed candidate, Lt. Gov. Janice McGeachin, lost her challenge to Gov. Brad Little, a fellow Republican. And in Oregon, Representative Kurt Schrader, a top moderate Democrat, was trailing his progressive challenger, Jamie McLeod-Skinner, in early vote tallies.

But Pennsylvania was the center of attention, a perennial presidential battleground that is seen as a bellwether of the nation’s political mood. The retirement of Senator Pat Toomey, a Republican, and term limits for Gov. Tom Wolf, a Democrat, meant rare simultaneous open races for both governor and Senate — and the latter could tip control of a chamber now evenly split 50-50 between the two parties.

Mr. Mastriano’s election denialism has been a key part of his appeal to the Republican base. Pennsylvania is one of three top presidential battlegrounds with a current Democratic governorship up for grabs in 2022 and a Republican-led Legislature that has promoted voter-fraud myths. The two other states are Michigan and Wisconsin.

In the Pennsylvania Senate race, Mr. Fetterman, whose progressivism and campaign-trail uniform of shorts and hoodies helped earn him the support of grass-roots voters and a passionate online donor base, won the Democratic primary, easily defeating Representative Conor Lamb, a moderate from outside Pittsburgh who was endorsed by Democratic officials statewide as the most electable candidate.

Mr. Fetterman was leading in every county on the state.

The Democratic primaries came to an unusual finish, with both leading candidates absent from the trail. Mr. Shapiro, 48, tested positive for the coronavirus and was isolating at home while Mr. Fetterman, 52, suffered a stroke on Friday and his campaign announced he had a procedure on Tuesday “to implant a pacemaker with a defibrillator.”

Both Democrats cast emergency absentee ballots.

Pennsylvania is outwardly a swing state, but Democratic strength has eroded in recent years. That has been clear in the difference between former President Barack Obama’s five-point victory in 2012 in the state and the much narrower, one-point presidential races in 2016 and 2020. Democrats, who have long led in party registrations, have seen their advantage slip to 550,000, down from 815,000 during the May 2018 primaries.

Whomever Mr. Fetterman faces, the Pennsylvania Senate race is expected to be among the fiercest and most expensive of the fall, with millions of dollars in television ads already reserved.

A hulking figure with a shaved head, tattoos and a goatee, Mr. Fetterman has cultivated an outsider image in part by refusing to court elected party officials and campaigning in rural counties where Democrats have suffered huge losses. When he met President Biden at the site of a collapsed bridge, he wore shorts. When he attended the White House Easter Egg Roll, he sported a sweatshirt.

Democratic voters embraced that style and Mr. Fetterman’s promise to win back support in the state’s conservative interior counties over the centrist polish of Mr. Lamb, as well as Malcolm Kenyatta, a liberal state legislator from the Philadelphia area.

“He looks like a gruff working-class Western Pennsylvania dude,’’ Brendan McPhillips, who ran Mr. Biden’s campaign in the state in 2020, said of Mr. Fetterman. “When he walks into a local dive bar, there’s a resonance there.”

Mr. Fetterman, who endorsed Senator Bernie Sanders’ presidential campaign in 2016, ran for Senate that same year, finishing a distant third in the primary.

The political climate nationally for Democrats in 2022 looks bleak. But many Pennsylvania Republicans are still openly worried about their party’s chances with a Mastriano-led ticket.

Mr. Mastriano, who has been subpoenaed by the congressional committee investigating the Jan. 6 riot, made his own failed effort to subpoena voting machines to “audit” the 2020 election. Last month he spoke at a conference organized by QAnon conspiracy theorists.

“He’s very far right,” said Tom Marino, a former Republican congressman in the state. “There will be moderate Republicans and independents and perhaps even some moderate Democrats in Pennsylvania that will not vote for Mastriano.”

Last-minute efforts to consolidate a deeply splintered Republican field and unite behind the leading Mastriano alternative in the polls, former Representative Lou Barletta, had mostly flopped even before Mr. Trump issued his endorsement. Mr. Mastriano was leading in a landslide, roughly doubling Mr. Barletta’s vote total.

Mr. Marino lashed out at Mr. Trump for not backing Mr. Barletta. Both Mr. Marino and Mr. Barletta had supported Mr. Trump in 2016. Mr. Marino said he was frustrated that the former president would spurn an early Trump supporter in favor of Mr. Mastriano. “With Trump, loyalty is a one-way street,” Mr. Marino said in an interview, “and I’ve learned that now.”

Mr. Shapiro made clear his preference, meddling in the Republican primary in the final weeks to boost Mr. Mastriano, an Army veteran who served in Iraq and Afghanistan, by running television ads that highlighted some of his conservative stances popular with the Republican base.

As of May 2, the Shapiro campaign had $15.8 million; the Mastriano campaign had less than $800,000, according to state records.

Mr. Shapiro has said he will make the fall election partly a referendum on abortion rights, given the likelihood that, in a post-Roe world, the Republican-led legislature will pass a bill strongly restricting abortion. Mr. Shapiro has said he would veto such a measure while Mr. Mastriano, who has made his Christian faith central to his candidacy, favors banning abortion with no exceptions for rape, incest or the mother’s health.

For much of 2022, the Republican Senate primary had been dominated by Dr. Oz and Mr. McCormick, who spent, along with allies, more than $45 million on television advertisements. Ms. Barnette spent less than $200,000 but used debates and her biography as a Black woman who was a “byproduct of rape” and who became an unabashed right-wing Republican to connect with the conservative base.

The Club for Growth, an anti-tax group, spent more than $2 million to give Ms. Barnette a late boost but an intense set of last-minute attacks, including from Mr. Trump appear to take a toll. “When she’s vetted, it’s going to be a catastrophe for the party,’’ the former president warned Monday.

She has notably not committed to backing her G.O.P. rivals in November. “I have no intention of supporting globalists,” she said on a Breitbart podcast on Monday.

Mr. Trump had originally endorsed Sean Parnell, a failed congressional candidate, for the seat last year, but Mr. Parnell quit the race after his estranged wife accused him of abuse. In April, Mr. Trump endorsed Dr. Oz after a heavy lobbying campaign by both Mr. McCormick, who served in the George W. Bush administration, and Dr. Oz.

A key figure in Dr. Oz’s camp was Sean Hannity, the Fox News host who regularly had the doctor on his program.

In his election night speech, Dr. Oz thanked, in order, his wife, Mr. Trump and Mr. Hannity. “He understands exactly how to make a difference and he’s been doing that this entire campaign,” Dr. Oz said of Mr. Hannity.

Mr. McCormick, whose wife was a senior Trump White House official, brought a bevy of Trump alumni onto his campaign team — a fact that Mr. Trump ridiculed at his lone rally with Dr. Oz.

“If anybody was within 200 miles of me, he hired them,” Mr. Trump said of Mr. McCormick.

Both Mr. McCormick and Dr. Oz were accused of carpetbagging. Mr. McCormick, who is from Pennsylvania, lived in Connecticut while leading Bridgewater, the hedge fund. Dr. Oz, who attended medical school at the University of Pennsylvania, moved back to the state from New Jersey in late 2020, according to his campaign, originally renting a home from his wife’s parents.

Dr. Oz faced hesitancy from conservative voters about his residency, his dual Turkish citizenship and previous positions that he took in interviews, on his TV show and in columns with his byline for gun restrictions and abortion rights. Those issues — along with the image of him kissing his Hollywood star — were aired relentlessly by a pro-McCormick super PAC.

Mr. Trump, who traveled to the state to hold a rally for Dr. Oz, was instrumental in building up the right-wing bona fides. At a rally on the eve of the election, Dr. Oz put Mr. Trump on speakerphone and held it close to the microphone, nodding along as the former president said, “He’s a loyal MAGA person.”

Nick Corasaniti contributed reporting from Chambersburg, Pa. Jazmine Ulloa contributed from Hendersonville, N.C.