MIAMI GARDENS, Fla. — President Obama on Thursday called Donald TrumpDonald John TrumpBiden adds to vote margin over Trump after Milwaukee County recount Krebs says allegations of foreign interference in 2020 election 'farcical'  Republicans ready to become deficit hawks again under a President Biden MORE “dangerous” for the country one day after the GOP nominee suggested he might not honor the result of the November presidential election.

“This is just more than the usual standard lie,” Obama told an energetic group of Hillary ClintonHillary Diane Rodham ClintonValadao unseats Cox in election rematch Trump says he'll leave White House if Biden declared winner of Electoral College Federal workers stuck it out with Trump — now, we're ready to get back to work MORE supporters during a rally here at Florida Memorial University, a historically black college.

“That is not a joking matter," he continued. "That is dangerous, because when you try to sow the seeds of doubt in other people’s minds about the the legitimacy of our elections, that undermines our democracy."

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The president spent nearly as much time bashing Sen. Marco Rubio (R-Fla.), who is facing a tough reelection challenge from Rep. Patrick Murphy (D-Fla.)      

But Obama’s main focus was taking down Trump, whose comments during the final presidential debate of 2016 caused a nationwide furor.

Many feared Trump’s unprecedented remarks could undermine America’s centuries-long tradition of peaceful political transitions or spark unrest after the contest is over.

Obama accused Trump of “doing the work of our adversaries for them” by refusing to commit to accepting the election’s outcome.

The Republican real estate mogul stirred the pot again Thursday, telling supporters in Ohio he “will totally accept the result of this great and historic presidential election.”

But then he paused and added, “If I win.”

Trump later opened the door to conceding the race to Clinton, the Democratic nominee, if she wins by an overwhelming margin, in which case he said he would accept a “clear election result.”

With Trump trailing in the polls, Obama is seeking to tie him to Republicans running in competitive down-ballot races.

The president is not just hoping to help Clinton win the White House, but also to boost Democrats’ efforts to win back the Senate, which would give her a better chance of advancing her agenda.

The president launched into a lengthy diatribe against Rubio for sticking by with Trump, despite the fact the senator dubbed the businessman a “con artist” who can’t be trusted with the nation’s nuclear codes during their vicious presidential primary fight.

“How can you call him a con artist and dangerous and object to all the controversial things he says but then say, ‘I’m still going to vote for him?’ Obama asked. “Come on, man.”

The president’s voice was virtually dripping with contempt as he rattled off a series of insults against Rubio over his Senate attendance record and his decision to abandon an immigration reform bill he worked on in the upper chamber.

Obama also sought to use Trump’s latest tactic as a tool to motivate Democrats to vote early in the Sunshine State, where ballots can be cast as soon as Monday.

The president repeatedly said there is no evidence of the voter fraud Trump has spoken about, but added that’s not enough to dispel talk of a rigged election.

“There’s only one way we lose this election: If we don’t turn out to vote,” the president said. “We’ve got to do it big; there has to be no doubt. Because the Donald is whining that the one is going to be rigged before the game is even over.”

He also used Trump’s words as another piece of evidence — along with allegations of sexual misconduct, mockery of a disabled reporter and crude language about minorities — that Trump is unfit to serve as commander in chief.

“Of course, today he said, ‘It’s not rigged if I win,’ ” Obama said. “He doesn’t even worry if what he says is true. This is just him worrying about him losing.”

—Updated at 5:57 p.m.