Arpaio was under investigation last year by the U.S. attorney for suspected abuse-of-power charges, but that inquiry was eventually dropped. The Department of Justice has also charged Arpaio's office with civil rights violations, arguing that the sheriff has systematically discriminated against Hispanics in Maricopa County.

Arpaio has also earned national attention for his efforts to argue that President Obama's birth certificate is a forgery. 

“My investigators believe that the long-form birth certificate was manufactured electronically and that it did not originate in a paper format as claimed by the White House," Arpaio said at a news conference last year.