Former Republican Congressman, Joe Walsh, once a backer of President Donald Trump, said he would mount a Republican primary challenge to the president because “we can’t take four more years of Donald Trump”.

Appearing on ABC’s “This Week,” the former Illinois congressman, now a radio talk-show host, called Trump “completely unfit to be president.”

He said he was launching his quixotic bid because “nobody in the Republican Party stepped up” despite what he described as deep dismay over Mr Trump’s performance.

“He’s nuts. He’s erratic. He’s cruel. He stokes bigotry. He’s incompetent. He doesn’t know what he’s doing.

“Everybody believes, in the Republican Party, everybody believes he’s unfit,” said Mr Walsh, a tea party stalwart with his own history of inflammatory comments who formerly represented a suburban Chicago district before losing his seat in 2012.

“He lies every time he opens his mouth,” Mr Walsh added.

Mr Walsh’s announcement that he would contest the 2020 Republican nomination followed a head-spinning week, even by the turbulent standards of Mr Trump’s administration. Over a period of days, the president engaged in a series of striking policy gyrations and a stream of provocative commentary.

With many economists citing signs that the economy could be tilting toward a recession, Mr Trump responded by touting the economy’s strength even as he repeatedly contradicted himself on tax policy, intensified trade war with China and excoriated his own appointed head of the Federal Reserve Board, Jerome H. Powell.

Along the way, he scrapped a visit to Denmark, a NATO ally, angered by the country’s firm rejection of his idea to buy the Arctic island of Greenland. He also denounced Democratic-voting Jews as “disloyal,” reviving a centuries-old anti-Semitic trope, and declared that he was “the chosen one.” He later insisted he had been joking.

Through it all, leading congressional Republicans were almost uniformly silent.

Mr Walsh said that left him convinced that the party was out of step with voter perceptions, despite polling that indicates strong support for Mr Trump among Republican voters.

Polls suggest the large majority of Republican voters approve of the direction in which Mr Trump has taken the party.

A significant minority disapproves, which could provide a base for a challenge, but because the Republicans have “winner take all” rules in many primaries, a challenger might end up with no convention delegates even if the candidate won a large share of votes.

The party’s national committee has thrown its machinery into high gear in support of the president, and Trump backers are in firm control of GOP party leadership in key primary states such as Iowa, New Hampshire and South Carolina.

Supporters say Mr Walsh, with his talk-show experience, will have a unique ability to rattle a president who devotes large amounts of attention to his image on television.

Mr Walsh insisted he was undaunted by the challenge. “The country is sick of this guy’s tantrum,” Mr Walsh, 57, said of Mr Trump, who is in Biarritz, France, this weekend for a meeting of the Group of Seven industrialised democracies. “He’s a child.”

In contrast to the crowded Democratic field, Mr Trump so far has faced only one GOP challenger, former Massachusetts Governor Bill Weld, who ran for vice president in 2016 on the Libertarian Party ticket.

Mr Weld said he thought it was “terrific” that Mr Walsh was entering the race, and called on others to jump in as well because more Republican candidates would lead to a more robust debate about the party’s direction.

“We need to assemble rational people,” Mr Weld said on NBC’s “Meet the Press.”

“Sure, a crazed president makes the stock market go down, but that doesn’t mean we have to like it.”

A few other Republicans have flirted with the idea of challenging Mr Trump, including former Representative Mark Sanford of South Carolina, Maryland Governor Larry Hogan and former Senator Jeff Flake of Arizona. Former Ohio Governor John Kasich, who ran against Mr Trump in the 2016 primaries, has also talked about a rematch but appears to have decided against it.

Mr Walsh has a history of rhetoric that has sometimes targeted ethnic, religious or racial minorities in a manner reminiscent of Mr Trump’s. In December 2016, he tweeted “Obama is a Muslim,” referring to the former president. In 2017, he said the country had held Mr Obama “to a lower standard cuz he was black.”

Asked about those statements, Mr Walsh told “This Week” host George Stephanopoulos that he now regretted them.

“I said some ugly things about President Obama that I regret,” Mr Walsh said, calling some of his own language “hateful.” He said he himself helped champion a political style that became a Mr Trump hallmark.

“Well, again, the beauty of what President Trump has done is, George, he’s made me reflect on some of the things I have said in the past,” he said. “I had strong policy disagreements with Barack Obama, and too often I let those policy disagreements get personal.”

Asked if he truly had believed Mr Obama was Muslim, he responded, “God, no.”

“I helped create Trump,” Mr Walsh told Stephanopoulos. “And George, that’s not an easy thing to say.” (tca/dpa/NAN)