Update: Former Rep. Joe Walsh announced Aug. 25 that he would challenge President Donald Trump in the 2020 Republican primary.

Previously:

Former GOP Rep. Joe Walsh has been making noise in recent days about a possible primary challenge to President Donald Trump in 2020.

Trump, Walsh wrote in a New York Times op-ed earlier this month, is not a good leader, but a “racial arsonist who encourages bigotry and xenophobia.”

Walsh should know.

The one-term former House member from Chicago, who now hosts a radio talk show, has a long history of making racist and incendiary comments, particularly about Barack Obama. He falsely accused the former president of being a secret Muslim who hates Israel and regularly questioned his birthplace ― a conspiracy theory also embraced by the current occupant of the Oval Office. Obama, Walsh further argued, only won the 2008 election because he is a “black man who was articulate.”

In 2016, after a police shooting in Dallas, Walsh promised “war” and warned Obama to “watch out,” alleging that he helped get “cops killed.” After the 2015 domestic terror attack in San Bernardino, California, he urged people to “do whatever we can to defeat Islam.” He was also briefly kicked off the air for using racial and ethnic slurs on his radio show.

Then there’s Walsh’s work boosting Trump during the 2016 election ― which he has since renounced as a mistake ― and his explosive Twitter account: