(AP) -- Fellow Republicans on Thursday condemned Donald Trump's refusal to agree to accept the outcome of the election. Even supporters distanced themselves, warning that Trump's stance could undermine the nation's democratic system.

Sen. John McCain of Arizona, the party's 2008 nominee for president, said that he didn't like losing to Barack Obama, but he accepted the results.

"I don't know who's going to win the presidential election. I do know that in every previous election, the loser congratulates the winner and calls them, 'my president,'" McCain said in a statement. "That's not just the Republican way or the Democratic way. It's the American way. This election must not be any different."

Sen. Pat Toomey of Pennsylvania, who is in a tough re-election contest, called Trump's stance "worse than unfortunate - it's irresponsible."

"When the people speak, the candidates need to accept the results - whatever they are," Toomey said, adding that he would be happy to accept the results of his own hard-fought race.

Gov. Scott Walker of Wisconsin said that Trump has to accept the results, and no matter what he does "all of the other elements of government will go forward."

"The bottom line is whether he does or doesn't, there's going to be a new president," Walker told WLUK-TV following an event in Green Bay.

During Wednesday night's debate against Hillary Clinton, Trump refused under direct questioning to agree to abide by the outcome of the election Nov. 8. "I will tell you at the time," he said, and "I will keep you in suspense."

Trump doubled down on the provocative and highly unusual stance Thursday, seeming to mock his detractors by declaring at a rally in Ohio that he will "totally accept" the results of the presidential election -- "if I win."

His comments shocked and alarmed Democrats and Republicans alike, and denunciations rained down from all sides as officials in both parties warned that Trump's comments risked undermining the nation's electoral system, depressing voter turnout on Election Day and even provoking dangerous unrest if Clinton is elected. For down-ballot Republicans running for House and Senate, it was just the latest occasion to distance themselves from their presidential nominee, whose endlessly provocative campaign risks costing his party control of Congress.

Sen. Mark Kirk of Illinois, who is behind in his own re-election race in a blue state, called the comments "another vivid example of why Donald Trump is unprepared and unfit to be commander in chief."

"Since the end of George Washington's presidency in 1797, our nation has peacefully and smoothly transitioned power from one president to the next. It is one of the hallmarks of our democracy," Kirk said. "Only someone as delusional as Donald Trump would believe he is the exception to this rule."

Sen. John Thune of South Dakota, a member of the Senate leadership who has gone back and forth on supporting Trump, said that "The American electoral process is the cornerstone of our democracy."

"Suggesting otherwise undermines an electoral system that is a model for nations around the world," Thune said.

Defenders were hard to find. Republican Wendy Long, who is an extreme longshot running against Democratic Sen. Chuck Schumer of New York, said by email Thursday that she agrees with Trump's contention that vote fraud could compromise the election. Long said she would defer judgment on whether she would accept the results of the election.

"I will accept it if and when I'm satisfied that fraud did not determine the outcome," she wrote.

Notably silent Thursday were the two top Republicans in congress, Senate Majority Leader Mitch McConnell of Kentucky and House Speaker Paul Ryan of Wisconsin. Both have endorsed Trump, although Ryan announced earlier this month that he would no longer defend or campaign for him, following the release of the "Access Hollywood" tape of Trump bragging about getting away with groping women because he's a celebrity. Despite multiple requests to their offices neither McConnell nor Ryan would comment Thursday on what Trump had to say about the election results.

That provoked criticism from Democrats who insisted the GOP leadership was obligated to denounce Trump's stance.

"Never before in our history has a major party candidate refused to accept the results of an election," said House Minority Leader Nancy Pelosi, D-Calif. "The deafening silence of Speaker Ryan and Sen. McConnell only worsens the lasting damage that will be caused by this unprecedented assault on our values as a nation."

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Associated Press writers Scott Bauer in Wisconsin, Kathy Matheson in Philadelphia, Michael Hill in Albany, New York, and Mary Clare Jalonick in Washington contributed to this report.