As recently as 2018, however, Mr. Walsh appeared to still be defending Mr. Trump against charges of racism. After Mr. Trump attacked three journalists, all of them black women, Mr. Walsh wrote on Twitter that Mr. Trump treated everyone poorly. “Not just black women,” Mr. Walsh said. “He’s not a racist. He’s a bully.”
Mr. Walsh’s campaign did not respond to a request for comment.
Those promoting Mr. Walsh’s challenge to Mr. Trump played down the problems with Mr. Walsh’s own checkered history and questioned whether he really believed the things he has said.
“He’s made it through a rough patch and he deserves to have a rough patch, given the things he said,” said William Kristol, the conservative writer and prominent “Never Trump” Republican who has been working over the past year to recruit a challenger. “I think he’s making it through and will be a real problem for Trump, in part because he voted for Trump and he’s a populist conservative.”
Others expressed deeper skepticism of Mr. Walsh’s potential impact on the race.
Ed Rollins, a veteran Republican strategist who supports Mr. Trump, said he did not believe Mr. Walsh to be a viable candidate in part because he said the vast majority of the Republican Party was not actually looking for an alternative to Mr. Trump, and in part because Mr. Walsh was “not a very good messenger.”
“He lacks credibility,” Mr. Rollins said. “In a national scene, no one knows who he is, and those who do recall that he was a controversial member of Congress who was defeated after one term.”
More broadly, strategists noted that defeating an incumbent president was difficult, if not impossible, and required a vast war chest as well as significant support.
“It’s hard to see Walsh having either,” Mr. Bolger said.
“It’s a rough, tough game,” said Mr. Rollins, adding, “He’s not going to be the guy.”