Herschel Walker filed paperwork on Tuesday to run for the U.S. Senate from Georgia. Walker was encouraged by former President Donald Trump to seek the Republican nomination. If victorious, Walker will face Democrat Raphael Warnock in 2022.

Walker’s opponents in the GOP primary would be agriculture commissioner Gary Black, construction firm owner Kelvin King, and former Trump national security official Latham Saddler.

Walker’s friendship with Trump dates back to the 1980s when Walker played for Trump’s New Jersey Generals in the United States Football League.

Questions remain about Walker’s mental health as he once threatened to kill his ex-wife, according to her sister, the Associated Press reports. Walker has been open about his struggles with Dissociative Identity Disorder. There have also been questions on whether or not Walker would be a good fundraiser or a good campaigner as the Republicans look to gain back the Senate seats they lost in the past election.

Walker has lived in Texas for a long period of time but changed his voter registration last week to an Atlanta house owned by his wife, Julie Blanchard. Walker has also repeated the false claims of voter fraud in the 2020 election.

As an NFL running back Walker twice played for the Dallas Cowboys (1986-1989, 1996-1997), Minnesota Vikings (1989-1991), Philadelphia Eagles (1992-1994), and the New York Giants (1995) and was voted to two Pro Bowls.

Walker won a national championship with the University of Georgia in 1980 and later a Heisman trophy in 1982.