Duke's announcement came Friday on his website.
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A registered Republican, he would be seeking an open seat vacated by Republican David Vitter.
Duke's announcement comes as Louisiana is grappling with deep racial tensions after the shooting death of a black man by white police officers and the killing of three law enforcement officers by a black man.
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A white supremacist, Duke served one term as a state representative representing suburban New Orleans more than two decades ago. He ran unsuccessfully for governor in 1991 against Democrat Edwin Edwards.
Duke is a convicted felon, pleading guilty in 2002 to bilking his supporters and cheating on his taxes. He spent a year in federal prison.