The devastating image of Republican front-runner Donald Trump bobbing and weaving on national television when asked simply whether he would repudiate the support of David Duke or the Ku Klux Klan was far from erased by his later disavowals.

It is presumably the reason House Speaker Paul Ryan felt obliged to insist on Tuesday that the Republican Party "does not prey on people's prejudices" and that its nominee "must reject any group or cause that is built on bigotry."

Ryan's claim of course ignores the long history of Republican Party power-building by inflaming racial bias and anti-gay bigotry. And it cannot hide the fact that Republican front-runner Donald Trump is electrifying and energizing the white supremacist movement. White nationalists have done robocalls promoting Trump's candidacy in Iowa, New Hampshire, Vermont, and Minnesota.

As Richard Cohen, president of the Southern Poverty Law Center, has said, "You can't help who admires you, but when white supremacists start endorsing you for president, you ought to start asking why."

Trump's anti-immigrant rhetoric is clearly one big reason. Trump's announcement speech, in which he denounced Mexican immigrants, thrilled white nationalists. Less than two weeks after his launch, the neo-Nazi news site The Daily Stormer endorsed him. Celebrating his victories on Super Tuesday, which were applauded as a "total blowout" by the Daily Stormer, Trump reiterated his insistence that he would build a massive wall on the southern border and force Mexico to pay for it.

Of course, his extremism isn't limited to anti-Latino rhetoric. Trump ardently promoted birtherism when he was flirting with a 2012 challenge to Barack Obama. And this time around, his pledge to create a "deportation force" to forcibly remove millions of undocumented people and his call for a ban on Muslim immigration to the U.S. have been fervently embraced by the racialist right.

Trump has supported white nationalists by giving them a national platform and fundraising opportunities. He has repeatedly re-tweeted praise for him from white nationalists, giving them a chance to be known by his more than six million Twitter followers. "It's amazing how many people I've met who have said, 'I just discovered these ideas six months ago,'" white nationalist Richard Spencer told Vice in December. "Trump has unquestionably brought people to our ideas."

Indeed, Trump's campaign has become "a great outreach tool" for the KKK and "a fundraising engine for White Nationalist media."

It should be no surprise that white nationalists are energized and empowered by Trump. Last summer the New Yorker reported that today's white nationalist activists are inspired "by their dread of a time when non-Hispanic whites will no longer be the largest demographic group in America." Spencer says Trump reflects "an unconscious vision that white people have -- that their grandchildren might be a hated minority in their own country. I think that scares us."

John Derbyshire, whose racially charged writing got him booted from National Review in 2012, recently slammed Marco Rubio for saying that the Republican Party is the party of diversity.

There goes another ten thousand votes, Marco. Everyone in this country who can say the word "diversity" without rolling his eyes, is already going to vote Democrat. The rest of us are up to here with diversity, and want a candidate who's as sick of the diversity rackets as we are. That would be Donald Trump.

Trump's derisive dismissal of "political correctness" has given people permission to openly trumpet views they may once have kept to themselves--and gives them a place to gather together. David Duke has encouraged listeners of his radio show to volunteer for Trump's campaign, telling them, "you're gonna meet people who are going to have the same kind of mindset that you have."

That may be true. In December the Washington Post's Max Ehrenfreund looked at social science on race and politics. "There's a good deal of evidence that white resentment of minorities is linked to support for Republican candidates, their policies and conservative ideology in America," said Robb Willer, a political psychologist at Stanford University.

Eric Knowles, a political psychologist at New York University, has found that "membership in the tea party increased respondents' perceptions of white identity over time," Ehrenfreund wrote. "Other researchers have found that its members tend to be more racist and xenophobic, after accounting for their belief in limited government and other conservative principles."

That may help explain, but not excuse, the cowardice demonstrated by so many Republicans who have declined to condemn Trump and pledged to support him if he becomes the nominee, not to mention those like Gov. Chris Christie and Sen. Jeff Sessions who have enthusiastically endorsed him. Republican officials helped create the conditions for Trump's rise by promoting the angriest voices in right-wing media when they thought it was to their political benefit. They would do well to think beyond the prospects for 2016 to the long-term impact on America of the forces Trump and his supporters are unleashing.

Matthew Heimbach, a 24-year-old white nationalist, told the Washington Post, "Donald Trump, whether he meant to or not, has opened this floodgate that I don't think can be restrained regardless of what happens in the 2016 elections."