Walsh's campaign will undoubtedly be an uphill battle. Polls show that more than 80 percent of Republicans support Trump, a reality Walsh acknowledged on Sunday.
"I'm running because [Trump is] unfit, somebody needs to step up, and there needs to be an alternative," Walsh said. "The country is sick of this guy's tantrum. He's a child. Again, the litany. He lies every time he opens his mouth. Look at what's happened this week. The president of the United States is tweeting us into a recession."
"I can tell you, George, that most of my former colleagues up on the hill, they agree privately with everything I'm saying publicly," Walsh added. "They're scared to death."
Joe Walsh will challenge Trump for the 2020 Republican presidential nominationwww.youtube.com
Walsh, a former Trump supporter, has since become of the president's most-outspoken critics on the right. On Sunday, he apologized for helping "create" Trump.
"I helped create Trump, there's no doubt about that, the personal, ugly politics," he said. "I regret that. And I'm sorry for that."
In a tweet announcing his candidacy, Walsh said that Americans "can't take four more years of Donald Trump.
Friends, I'm in. We can't take four more years of Donald Trump. And that's why I'm running for President. It won'… https://t.co/y3yqp2OqPP— Joe Walsh (@Joe Walsh) 1566738249.0
Walsh is not the only Republican challenging Trump. Bill Weld, the former governor of Massachusetts, announced his candidacy in April. Both Walsh and Weld are long shot candidates.