Former Ku Klux Klan leader David Duke said Friday he would be Donald TrumpDonald TrumpKinzinger says Trump 'winning' because so many Republicans 'have remained silent' Our remote warfare counterterrorism strategy is more risk than reward Far-right rally draws small crowd, large police presence at Capitol MORE's number one supporter in the Senate. 

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Duke, who announced last month he would run for Louisiana's open Senate seat, said he is 100 percent behind Trump's legislative agenda. 

"As a United States senator, nobody will be more supportive of his legislative agenda, his Supreme Court agenda than I will," Duke said in an interview on NPR's "Morning Edition." 

"I'm 100 percent behind it. I have a long record of being in favor of protecting our borders from this massive immigration." 

Duke is an enthusiastic supporter of Trump, once calling him the "white knight" for "European American" interests. 

But his endorsement of Trump snared the candidate in controversy earlier this year.

Initially, Trump appeared to sidestep questions about Duke's support, but the GOP nominee later said he disavowed his endorsement.

Trump quickly rebuked Duke's Senate run, noting that he was criticized for not doing it fast enough when he received the initial endorsement in February. 

When asked last month if he would support a Democrat over Duke, Trump said "I guess, depending on the who the Democrat is — but the answer would be yes." 

Other Republican organizations, including the National Republican Senatorial Committee, have said they won't support Duke's run. 

Duke is running to replace retiring Sen. David Vitter (R), bringing the total number of Republicans in the primary field to 22. 

Updated at 10 a.m.