Donald Trump is the Republican nominee for president, and David Duke is running to represent Louisiana in the U.S. Senate. These facts are separate but related, and Duke, who is best known for being the former Grand Wizard of the Ku Klux Klan (KKK), admitted as much in his campaign announcement.

"I'm overjoyed to see Donald Trump and most Americans embrace most of the issues that I've championed for years. My slogan remains America first," he said, adding that he believes his "time has come" and that he intends to defend the rights of "European-Americans."

Duke joins two dozen candidates vying for U.S. Sen. David Vitter's seat. His chances aren't good but they are more than zero, and Trump is the reason. Duke's campaign marks the evolution of an election cycle tainted by nationalist xenophobia.

It's little secret that many White supremacists have embraced Trump as one of their own.

Matthew Heimbach, who founded the Traditionalist Workers' Party and is arguably the most prominent young White supremacist in the U.S. today, regularly attends Trump rallies and even assaulted a protester at one of them. The National Policy Institute's Richard Spencer also publicly supports Trump. Lest there be any doubt about his positions, consider that Spencer has called for non-Whites to be sterilized and wishes to create a European "ethno-state" in the U.S.

"[Trump] seems to genuinely care about the historic American nation that is White people," he told Vice in an interview.

And Heimbach and Spencer aren't necessarily outliers. The Trump campaign has enjoyed the support of the so-called "alt right" almost since its genesis, a reflection of the rhetoric that first propelled him to the top of the polls. Trump became a serious electoral candidate precisely because he incorporated racist stereotypes about Mexicans into a stump speech. Subsequent proposals to ban Muslim immigration only cemented his status as the GOP's likely nominee.

America's White supremacists understand that these proposals are dog-whistles. And as primary season advanced, so too did racist rhetoric on and offline.

Anti-Semitic harassment from self-identified Trump supporters has become so severe that the Anti-Defamation League set up a task force to assist affected Jewish journalists. On more than one occasion, Trump himself retweeted material from White supremacist accounts. And at last week's Republican convention, some hapless staffer included a pro-Trump tweet from on an official ticker. For the blessedly ignorant: is an anti-immigrant site named for English colonist Virginia Dare (irony is dead, long live irony).

If Duke thinks this has created the perfect climate for a Senate run, he's correct.

And it's difficult to overstate exactly how remarkable that is: Duke's political career is in shambles. He did successfully win a seat in the Louisiana state legislature in 1989, but failed to parlay that victory into a successful gubernatorial run in 1991. He lost badly to his Democratic challenger, partially because the state Republican party refused to support his run. Party apparatchiks denounced his ties to the KKK and endorsed his opponent with the slogan "Vote For the Crook: It's Important."

The GOP's official position on Duke hasn't changed. Reince Priebus denounced him almost as soon as he announced his run; so too did the state GOP and even Trump. In an interview with NBC's Chuck Todd, the nominee offered lukewarm support for Duke's hypothetical Democratic opponent. "I guess, depending on who the Democrat (is) — but the answer would be yes," he said.

But it's difficult for the GOP to truly distance itself from Duke.

In 2014, The New York Times asserted that Duke's views had already become part of "mainstream" Louisiana politics. As a state legislator, he filed bills that repealed certain affirmative action programs and made it more difficult for low-income people to access public housing.

He also has ties to sitting officials. U.S. Rep. Steve Scalise (R-La.) spoke to one of Duke's organizations in 2002 and reportedly told a journalist he was "like David Duke without the baggage." Scalise successfully weathered the revelations and remains in office. And Tony Perkins, who heads the Family Research Council and spoke at the RNC last week, purchased one of Duke's mailing lists on behalf of a campaign he was managing at the time.

And though Trump currently disavows Duke, he was previously slow to denounce the former Grand Wizard. He refused to outright reject Duke's support for his candidacy during an appearance on CNN's "State of the Union" and only issued a firm disavowal days later, under pressure.

To be clear, David Duke and Donald Trump don't share identical philosophies. Duke, for instance, is a Holocaust denier—and there's no evidence Trump shares that view.

But despite their differences, they need each other.

Trump owes his current success partially to the work of Duke and his fellow travelers. White supremacists have anchored the far-right end of the political spectrum for well over a century. They nurtured the racial paranoia Trump's campaign has so expertly tapped.

And Duke in turn owes Trump. His career died because it isn't politically expedient to be publicly affiliated with the KKK—and Trump may have begun to change that. He's certainly shifted the Overton window just enough for Duke's campaign to be something other than a total farce. Duke still isn't likely to win state-wide election, but he's not wrong to think that public sentiment tilts in his favor far more than it did a year ago.

This is the gate Trump has opened, with the full-throated blessing of the Republican base. Trump has sewn the wind. Duke, or someone very like him, may just reap the whirlwind.