David Duke has a long history in politics and the white supremacy movement. Here are key moments in Duke's life in the public eye. (Claritza Jimenez/The Washington Post)

Former Ku Klux Klan leader David Duke is running for the U.S. Senate, linking his decision to Donald Trump’s bid for the presidency and the business mogul’s proposals on trade and immigration.

Duke, a vocal Trump supporter, announced his candidacy for the seat in Louisiana on Friday and said he was “overjoyed” to see the businessman’s campaign  “embrace most of the issues that I’ve championed for years,” including the nationalist and protectionist notion of “America First.”

“We must stop the massive immigration and ethnic cleansing of people whose forefathers created America,” Duke said in a video posted to his website one day after Trump claimed the Republican presidential nomination.

The former KKK grand wizard’s entry into the race could prove problematic for Trump by serving as a reminder that earlier in the year, Trump failed to immediately repudiate Duke after he endorsed Trump’s campaign.

Duke said his goal is to represent what he described as white interests on Capitol Hill.

“Thousands of special-interest groups stand up for African Americans, Mexican Americans, Jewish Americans, et cetera, et cetera,” Duke said. “The fact is that European Americans need at least one man in the United States Senate — one man in the Congress — who will defend their rights and heritage.”

Duke represented suburban New Orleans in the Louisiana statehouse between 1989 and 1993 and ran unsuccessfully for Congress and the Louisiana governorship. In December 2002, he pleaded guilty to felony fraud and tax-evasion charges, and he was sentenced to 15 months in federal prison in April 2003. He was released after a year.

If elected, Duke would succeed Republican David Vitter, who is not seeking reelection after losing his bid for the governorship last year. Duke is one of nine Republicans running for the seat in a field of 23 candidates that includes GOP Reps. Charles W. Boustany Jr. and John Fleming.

“There are a lot of strong conservative candidates in the race, but he remains a visible person with name recognition around the country,” Louisiana State University political-communication professor Martin Johnson said in an interview. “In that sense, maybe he peeks his head above the pack.”

At the same time, Louisiana voters might hesitate, given Duke’s racial views, “even if there are elements of his message that resonate with them.”

“Goodness gracious, the guy is a Holocaust denier,” Johnson said. “He is hard to support, and he should be.”

The announcement makes Duke a high-profile character in the unfolding drama of an election season defined by racial animosity. Trump, who has repeatedly painted undocumented immigrants as a threat to America’s safety and has strongly defended law enforcement, is running amid several episodes of lethal violence by police against African Americans.

One recent episode took place in Baton Rouge, leaving a 37-year-old black man, Alton Sterling, dead after an encounter with police officers. Almost two weeks  later, three Baton Rouge police officers were shot and killed in what investigators describe as an ambush by a black man who targeted them. Two of the officers killed were white; one was black.

Duke did not specifically address the events in his home state Friday, although they have been frequent topics for him on Twitter, where he has about 12,500 followers.

“I believe it’s time we start talking about the reality of terrorism linked to Black radicals,” Duke tweeted July 17 after the news broke about the police shootings in Baton Rouge. “How is this any different than ISIS?”

Duke’s campaign is likely to raise further questions for Trump, who falsely claimed earlier in the year that he knew nothing about Duke when asked by CNN if he would disavow the white nationalist leader. After several days of controversy, Trump ultimately denounced Duke, but his equivocation drew criticism from Democrats and from Republicans, such as House Speaker Paul D. Ryan (Wis.), who said the matter should have prompted “no evasion” from the candidate.

Trump’s response to Duke’s announcement will be telling. “If Donald Trump is vague or mixed about Duke’s candidacy, it is possible that a lot of voters will make an association, particularly on the anti-immigrant message,” Johnson said.

Duke’s candidacy could also reawaken past controversy for House Majority Whip Steve Scalise (R-La.), who acknowledged in December 2014 that he spoke to a white-supremacist group founded by Duke in 2002. Scalise denied being involved with the group but was widely criticized for the speech.

The Republican campaign establishment and the Louisiana GOP rushed to distance themselves from Duke on Friday.

“We will not support David Duke,” National Republican Senatorial Committee Executive Director Ward Baker tweeted. “Several GOP candidates in [Louisiana] will have a great impact on our country. He is not one of them.”