Duke, 66, is a former Louisiana state legislator and unsuccessful Republican candidate for governor who served a 15-month federal prison sentence after pleading guilty in 2002 to charges of tax evasion and mail fraud.
Republican presidential nominee Donald Trump drew criticism in February for failing to quickly disavow support from Duke.
“I believe in equal rights for all and respect for all Americans,” Duke said in a video posted on his website. “However, what makes me different is that I also respect and demand the respect for the rights and heritage of European Americans.”
Friday was the deadline for U.S. Senate candidates from Louisiana to register. Online records posted by the Louisiana secretary of state’s office did not show any application from Duke as of midday.
Louisiana does not hold party primaries. Instead, candidates from all parties are placed on the same ballot. If no one receives a simple majority, the top two enter a runoff.