WASHINGTON (Reuters) - Joe Walsh, a conservative former U.S. congressman turned talk show host, said on Thursday he was leaning toward a Republican primary challenge to President Donald Trump, calling him a liar and a bully who is unfit for office.

The long-shot bid for the party’s nomination by Walsh, 57, who served one two-year term in Congress, is unlikely to make a dent in the president’s popularity among Republicans, which has remained consistently strong.

Trump has consolidated his grip on the party’s national and state machinery, and a Reuters/Ipsos poll conducted this week showed 87% of Republicans approve of his performance in office.

William Weld, a former Massachusetts governor, is so far the only Republican trying to unseat Trump, and his candidacy has failed to gain traction. Former U.S. Representative and South Carolina Governor Mark Sanford said in July he was considering a primary challenge because of the rising federal debt.

Walsh said in an interview with CNN on Thursday he was leaning toward challenging Trump, and indicated he would make a decision within a week or so.

“Trump’s a bully. And he’s a coward. And the only way you beat a bully and you beat a coward is to expose them, is to punch them,” he said in the interview.

“I think a good challenger can win. Only if they make the moral case. This guy’s unfit, he lies every time he opens his mouth.”

The White House did not comment on Walsh’s remarks, and the Trump campaign did not reply to a request for comment.

Walsh won a House of Representatives seat from Illinois as a candidate of the Republican Party’s fiscally conservative Tea Party movement in 2010, but was defeated by Democrat Tammy Duckworth in his 2012 re-election bid. After leaving Congress, he became a Chicago-area radio talk show host.

Walsh said he supported Trump during the 2016 election but became disillusioned, then disgusted, by the president.

The tipping point, he told CNN, was when Trump sided with Russian President Vladimir Putin over U.S. intelligence agencies on the topic of Russian meddling in the U.S. election after their meeting in Helsinki, Finland, last summer.

“That was it. That was ugly. That was disloyal,” he said.

Walsh called for a primary challenge to Trump in a New York Times opinion piece last week in which he criticized the president as an inveterate liar, citing Trump’s assertion that tariffs were being paid for mostly by China, not Americans. He also criticized Trump as reckless on fiscal issues, ineffective on border concerns and “clueless” on trade.

In the same article, he said he said he regretted questioning Democratic former President Barack Obama’s truthfulness about his religion and expressing hate for his political opponents.

“We now see where this can lead,” he wrote.

On Thursday, he admonished his fellow Republicans for inaction.

“This is a scary time. And if Republicans stay silent in the face of this guy, I don’t think the country will ever forgive the Republican Party,” he said.

“But forget about the Republican Party, if this guy gets four more years, we’re in real trouble. It’s worth doing anything you can do to try to stop that.”