Gregory Korte

USA TODAY

WASHINGTON — President Obama tied Republican candidates up and down the ballot to GOP presidential candidate Donald Trump on Thursday, rebuking Trump for claiming he'd only accept the result of the November election if he wins.

"This is more than just the usual standard lie," Obama said. "That's no laughing matter.'

Obama said Trump has alleged voter fraud "without a shred of evidence."

"That is dangerous because when you try to sow the seeds of doubt in people's minds about the legitimacy of our elections, that undermines our democracy," he said. "You're doing the work of our adversaries for them because our democracy depends on people knowing that their vote matters. That those who occupy the seats of power were chosen by the people."

Obama's remarks, to a Hillary Clinton rally at Florida Memorial University, seemed to reflect a shift in Obama's campaign strategy as he plays an unusually active role in campaigning for his preferred successor, Hillary Clinton. At the Democratic National Convention and throughout the campaign, Obama has tried to drive a wedge between Trump and Republicans, saying Trump's ideas were neither Republican nor particularly conservative.

But with Trump's poll numbers dropping, Obama is now trying to tie Republican candidates to their presidential nominee.

Trump: I'll accept the election results — 'if I win'

Obama said most Republicans abandoned Trump after the release of the Access Hollywood tape in which Trump was caught on microphone describing what he wanted to do to a female television personality. Those remarks, Obama said, "qualify as sexual assault."

"Apparently that was the deal breaker for them. Or at least, his poll numbers dropping after the tape came out was the deal breaker for him," he said. "But here's my question: Why would it take you this long to figure out that Donald Trump shouldn’t be president?"

"If you made a career out of idolizing Ronald Reagan, then where were you when your party's candidate for president was kissing up to Vladimir Putin, the former KGB officer?" he said. "You’re O.K. with your nominee having a bromance with Putin."

Obama argued that Republicans are willing to look the other way when Trump does something they've often criticized Obama for.

"You say you love the Constitution. In fact, you say Obama is overreaching with his executive actions, he's violating the Constitution, should be impeached. But then you stand up and nominate and support a guy who says that he would silence reporters, jail his political opponent in the middle of a debate, deport whoever he wants," he said.

Speaking in the battleground state of Florida, Obama spent almost as much time blasting Sen. Marco Rubio as he did going after Trump. Noting that Rubio had called Trump a "dangerous con man," Obama said he was confused about how Rubio was still voting for Trump over Clinton.

"That is the height of cynicism," Obama said. "That's the sign of a man who will do anything, say anything, pretend to be anybody just to be elected."