Story highlights Arpaio has served as the top cop in Phoenix's Maricopa County

Arpaio called himself "America's toughest sheriff"

Washington (CNN) Joe Arpaio, the poster child for hardline immigration policy in the United States, has lost his reelection run for sheriff in Arizona's largest county, according to an Associated Press projection.

CNN is not independently projecting a winner for this race.

Arpaio has served as the top cop in Phoenix's Maricopa County for decades and was seeking his seventh term on Tuesday. But he lost to Democrat Paul Penzone, a former Phoenix policeman.

Arpaio called himself "America's toughest sheriff" and was known for his tough stance on immigration in the border state. His reelection run was imperiled, though, when a federal judge ordered him to be tried on a criminal contempt charge, accusing him of disobeying a court order in a racial-profiling case.

A staunch supporter of Donald Trump, Arpaio has insisted that President Barack Obama is not a US citizen and that his birth certificate is fraudulent.