"What better way to continue fighting ... for the people of the United States and to continue to defend democracy," Harry Dunn said in an interview on MSNBC.

The announcement on the eve of the three-year anniversary of the violent attack came as the former Republican president again seeks the White House after his 2020 loss to Democrat Joe Biden. Biden has also cast this year's contest as critical to democracy's survival as he and Trump prepare for a rematch in November.

Dunn, a 15-year veteran of the police force that protects U.S. lawmakers, has been vocal about the physical and racist abuse he endured during the attack as Trump supporters sought to prevent Congress from certifying Biden's 2020 victory, including before a bipartisan House of Representatives panel that investigated the deadly riot.

He is seeking to replace retiring U.S. Representative John Sarbanes of Maryland, a Democrat, as Democrats seek to win back the majority in the chamber. Dunn resigned from the police force last month, NBC reported.

Trump, the frontrunner for the Republican presidential nomination, has not been charged with any crimes related to fomenting an insurrection or rebellion and has pleaded not guilty to criminal charges in federal and state courts for attempting to subvert the 2020 election.

He has called Jan. 6 a "protest" and vowed to pardon at least some of those who have been charged, convicted or pleaded guilty if he wins the presidency. So far, more than 1,200 people have been charged in the attack in which about 140 police officers were assaulted and seven people died.

Five Republicans are challenging Trump for the nomination, but have largely steered clear of mentioning Jan. 6, with two rivals -- Nikki Haley and Ron DeSantis -- promising to pardon Trump if he is convicted of any crimes.

Since the attack, Republicans have become more sympathetic to the rioters and less likely to blame Trump for his actions that day, a Washington Post-University of Maryland poll this week showed.

Dunn urged voters to take Trump's authoritarian language during his campaign seriously, telling MSNBC: "We are one election away from the extinction of democracy as we know it."

Representatives for Trump did not immediately respond to a request for comment.

(Writing by Susan Heavey; editing by Jonathan Oatis)