Donald Trump said on Thursday he would accept the result of the Nov. 8 election — “if I win” — fueling Republican concerns his stance would make it harder for his party to maintain control of Congress.

His refusal to commit to accepting the election outcome was the standout remark of the third and final 2016 presidential debate between Trump and Democratic rival Hillary Clinton on Wednesday night. It ratcheted up Trump’s allegations the election was being rigged against him, and became the latest flashpoint in an unusually acrimonious race three weeks before voters go to the polls.

Clinton called the comment “horrifying.”

President Barack Obama blasted Trump on Thursday at a rally in Miami Gardens, Florida, for Clinton and U.S. Rep. Patrick Murphy, who is trying to unseat Republican Sen. Marco Rubio, a Trump supporter.

“That is dangerous. Because when you try to sow the seeds of doubt in people’s minds about the legitimacy of the elections, that undermines our democracy. Then you’re doing the work of our adversaries for them,” Obama said.

Maine Gov. Paul LePage also had some sharp words for Trump during a radio appearance on WGAN on Thursday.

“Donald, take your licks and let’s move on four years. … Not accepting the result is just, it’s a stupid comment,” the Republican governor said. “Get over yourself.”

LePage, who said this week that Maine’s election system is illegitimate because voters here are not required to show a photo identification at the polls, stopped short of endorsing Trump’s contention that the election is rigged against him, but said he believes the media is.

“I do believe that the American media has given Hillary Clinton a free pass,” he said, referring to the release of emails by WikiLeaks. “I think the Hillary Clinton campaign is a criminal enterprise and she’s getting away with it. She’s buying the country. … The problem is it’s not so much what [media coverage] Donald Trump is getting. It’s what Hillary isn’t.”

Trump modified his comment at a rally in Ohio on Thursday, but did not back off.

“I would like to promise and pledge to all of my voters and supporters and to all of the people of the United States, that I will totally accept the results of this great and historic presidential election — if I win.”

He added he would accept “a clear election result, but “reserve my right to contest or file a legal challenge in the case of a questionable result.

With Trump trailing in opinion polls, the focus ahead of the Nov. 8 vote is shifting to whether Republicans can keep their narrow majority in the Senate or even their larger advantage in the House.

Sen. John McCain of Arizona, who lost the 2008 presidential election to Obama, said accepting the election result was “the American way.”

“I didn’t like the outcome of the 2008 election. But I had a duty to concede, and I did so without reluctance,” McCain, who has opened a poll lead in his Senate re-election race, said in a statement. “A concession isn’t just an exercise in graciousness. It is an act of respect for the will of the American people, a respect that is every American leader’s first responsibility.”

McCain has withdrawn his support for Trump.

Asked on Wednesday night if he would commit to a peaceful transition of power, Trump, a businessman-turned-politician, replied: “What I’m saying is that I will tell you at the time. I’ll keep you in suspense. OK?”

Trump’s statement, the most provocative in a debate that repeatedly descended into rancor, made headlines across the country and raised questions about his commitment to a peaceful transition of power, a cornerstone of American democracy.

Clinton accused Trump of being Russian President Vladimir Putin’s puppet. Trump called Clinton a “nasty woman” and a criminal who should be barred from running. They did not exchange the customary handshake when the debate ended.

Democrats jumped to ask Republican candidates whether they agreed with Trump, who is making his first run for public office against Clinton, a former senator and secretary of state.

“Do you agree with Donald Trump to question the results of the election?” the Nevada Democratic Party asked in a release targeting Republican Joe Heck. Heck is in a tight race with Democrat Catherine Cortez Masto for retiring Democratic leader Harry Reid’s Senate seat.

Republican consultant Matt Mackowiak said down-ballot candidates would distance themselves from Trump’s comment, but it was a problem that the issue had drowned out everything else that came up on Wednesday.

“The real cost is that the post-debate discussion has been consumed by this, and not by his overall very good debate performance and the problems Hillary created for herself on a range of issues,” Mackowiak said.

Trump’s comments did not worry his supporters.

Marion Fields, 48, a registered Democrat who backs Trump, said he did not think concession would be an issue because Trump would win. Were he to lose, “After it’s announced, you’d have to be a professional and concede.”

A CNN/ORC snap poll said 52 percent of Americans thought Clinton won the debate, to 39 percent for Trump.

Trump donor and energy investor Dan Eberhart said Trump won. He disagreed with his rhetoric, but still backs the candidate.

“I think Hillary’s policies and track record are not what the country needs leading us forward for the next four years. And that backs me into supporting Trump,” Eberhart said.

An estimated 71.6 million people watched the final debate on TV on Wednesday, below the audience for their first encounter but the third-largest total ever recorded.

The data supplied by the Nielsen ratings agency on Thursday covered people who watched Wednesday night’s debate on the four main U.S. broadcast networks plus nine cable and public television channels.

The first Clinton-Trump face-off in September attracted a total TV audience of 84 million, the largest in the history of U.S. presidential debates.

Last week’s second debate, which was broadcast opposite popular “Sunday Night Football,” was seen by 66.5 million.

Wednesday’s audience ranked as the third-highest for a U.S. presidential debate since Nielsen started collecting TV viewership figures for the encounters in 1976. A 1980 debate between Democratic President Jimmy Carter and Republican challenger Ronald Reagan drew 80.6 million viewers.

Nielsen data reflect only those who watched the debate on TV at home and did not include millions more who watched online, through social media or in bars and restaurants.

Trump campaign manager Kellyanne Conway sought on Thursday to defend Trump, saying in television interviews he was “putting people on notice” about voting irregularities.

Trump has stepped up allegations that the election is being rigged against a backdrop of accusations that he had made improper sexual advances to women since a video emerged two weeks ago in which Trump boasted of such behavior.

A 10th woman came forward on Thursday at a news conference in Manhattan with lawyer Gloria Allred, a Clinton supporter who specializes in representing women in cases of alleged assault.

Trump campaign spokeswoman Jessica Ditto called the news conference a “coordinated, publicity-seeking attack” by Allred.

Trump has not offered specific evidence to back up his vote-rigging claims, and numerous studies have shown that the U.S. election system, which is run by the states, is sound.

BDN writer Christopher Cousins contributed to this report.