Republican Joe Walsh announces he will primary Trump in 2020

"We've got a guy in the White House who’s unfit, completely unfit, to be president. And it stuns me that nobody stepped up, nobody in the Republican Party stepped up, because I’ll tell you what, George, everybody believes in the Republican party, everybody believes that he’s unfit."

"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 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."

The big picture: Walsh isn't Trump's only primary challenger, as former Gov. Bill Weld (R-Mass.) has already launched a long-shot bid. But the Tea Party Republican would likely offer a different approach to the more traditional Weld, having created a brand for himself as a conservative activist unafraid to ruffle feathers. That has led Walsh to his fair share of controversy, including allegations of racist statements.

• Walsh apologized for calling President Obama a "Muslim" and a "traitor," telling ABC: "I had strong policy disagreements with Barack Obama and too often I let those policy disagreements get personal."
• Walsh laid the groundwork for a run at the presidency in a NY Times op-ed last week in which he stated the case for a contender from the right to challenge Trump. In the op-ed, Walsh said he gave Trump "a fair hearing" after voting for him in 2016, but he realized soon after he became president that he couldn’t support him.

The bottom line: President Trump has a near-90% approval rating within the Republican Party, and it will be incredibly difficult for Walsh or any primary challenger to replace him as the nominee.

Go deeper: Trump challenger Joe Walsh has an inflammatory record of his own