'They've been riding this tiger for a long time: President Obama takes aim at Republicans who are trying to desert Donald Trump, accusing them of 'filling a swamp of crazy'

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President Barack Obama slammed Republicans who are disavowing Donald Trump by saying they deserve no credit for their sudden change of heart after having 'stood by silently' for so long.

Obama accused Republicans of filling a 'swamp of crazy' by allowing unfounded and hate-filled rhetoric to go unchallenged within the party for years.

Campaigning for Democrats in Ohio, the President said most Republicans aren't like Trump and 'know better,' but hadn't renounced the kind of rhetoric Trump embraces out of deference to the Republican base. 

President Barack Obama slammed Republicans who are disavowing Donald Trump by saying they deserve no credit for their sudden change of heart after having 'stood by silently' for so long

He then said it was GOP complacency that led the party to nominate a candidate who he said brags and jokes about sexually assaulting women.

'You can't wait until that finally happens and then say, "That's too much, that's enough", and then say somehow you are showing some type of leadership and deserve to be elected to the United States Senate,' Obama said. 

'In fact, I'm more forgiving of the people who actually believe it than the people who know better and stood silently by out of political expediency.'

Obama's attempted take-down of Republicans seeking distance from Trump was the clearest signal to date of the strategy Democrats plan to deploy in congressional races in the final weeks of the campaign.

Obama accused Republicans of filling a 'swamp of crazy' by allowing unfounded and hate-filled rhetoric to go unchallenged within the party for years 

The President said it was GOP complacency that led the party to nominate a candidate who he said brags and jokes about sexually assaulting women

Across the country, dozens of Republicans up for re-election have called for Trump to step down as nominee or have renounced their support, hoping to spare themselves the fallout of Trump's sexually aggressive comments about women. 

They include prominent senators like Kelly Ayotte of New Hampshire and John McCain of Arizona — who both face tough re-election challenges.

But Democrats are working to tie those Republicans to Trump nonetheless, in large part by arguing their last-minute denunciations are too little, too late.

Obama said 'all that bile, all that exaggeration' from Republicans had bubbled up over the years and that Trump, just like one of his skyscrapers, had 'just slapped his name on it and took credit for it.'

'You can't wait until that finally happens and then say, "That's too much, that's enough", and then say somehow you are showing some type of leadership and deserve to be elected to the United States Senate,' Obama said

A young boy reaches over the top of a crowd of people to try to grab President Obama's hand after a rally in Columbus, Ohio

'The problem is not that all Republicans think the way he does,' Obama said. 'The problem is that they've been riding this tiger for a long time. They've been feeding their base all kinds of crazy for years.'

As his case study, Obama chose Republican Sen. Rob Portman of Ohio, who is working to fend off a challenge from Democratic former Gov. Ted Strickland. 

Though Democrats had expected the race to be one of their better prospects to win a GOP-held Senate seat, Strickland has been running consistently behind Portman in the polls.

'People like Ted's opponent, who know better, have stood silently by,' Obama said. 'This is the nominee you get. You make it possible.'

Obama noted that Portman had revoked his support for Trump, but not until video emerged late last week of Trump bragging about kissing women without their permission and groping them. 

'The problem is not that all Republicans think the way he does,' Obama said. 'The problem is that they've been riding this tiger for a long time

President Obama will be out campaigning for Hillary Clinton on Friday as well, capping off a two-day stretch that saw him hit the trail

Obama said that meant Portman hadn't been sufficiently bothered by Trump's previous remarks about Mexicans, Muslims, Gold Star mothers and disabled people.

'Why was that OK?' asked an incredulous Obama. 'And now he says he'll vote for the vice presidential nominee instead,' he added, referring to Mike Pence. 'Except that guy still supports Donald Trump.'

Obama's remarks came at the start of a two-day visit aimed at revving up Democrats in Ohio, one of the few remaining swing states late in the campaign. 

On Friday, Obama will hold a rally in Cleveland for Clinton emphasizing early voting, a major focus for Democrats across the U.S.

This week Obama entered the final 100 days of his presidency, and he's increasingly devoting his time to trying to push Clinton over the finish line in the presidential race. 

With Trump and Republicans threatening to undo much of what Obama has accomplished over the last eight years, campaigning for Democrats is the most productive way for Obama to try to protect his legacy.