Former Illinois congressman and current talk radio host Joe Walsh announced Sunday he will challenge President Donald Trump for the 2020 Republican presidential nomination.

“I'm running because he's unfit,” Walsh told George Stephanopoulos, host of ABC’s “This Week.” “Somebody needs to step up, and there needs to be an alternative.”

Walsh is the second Republican to announce a challenge to Trump. The first is former Massachusetts Gov. Bill Weld, who announced his long-shot White House bid in April. Walsh is also considered a long shot.

Weld said on NBC's "Meet the Press" he is "thrilled" about Walsh's entry and is looking forward to more candidates potentially joining in the race.

Walsh had been working toward an announcement in recent days, claiming the party wants an alternative to Trump. On Sunday, he said he stepped up to run because the GOP "wants Trump gone" and "believes he's unfit."

"They don't have an alternative," he said. "I’ll tell you what, George — and look, I’m running because he's unfit. Somebody needs to step up and there needs to be an alternative. The country is sick of this guy's tantrum. He’s — he's a child."

Once a defender of the president on his conservative talk show, Walsh responded to a question about how his listeners are responding to his recent critiques of Trump. He told Stephanopoulos Trump's "supporters, I think, are tired of this." He said he also hears support for the president because "it's difficult to be a critic of the president in conservative talk radio."

On his show, Walsh said he got into battles that were beyond policy that were "hateful." He apologized for saying "some ugly things about President Obama that I regret" and that Trump has made him reflect on past statements.

Asked if he is the best messenger to make a case against Trump's reelection, Walsh said: "I helped create Trump. And George, that's not an easy thing to say.

"I feel responsible for this. But I'm a conservative, and I think there's a decent chance to present to Republican voters a conservative without all the baggage," he said.