But he has since soured on Trump, criticizing the president over growth of the federal deficit and writing in a New York Times column that the president was "a racial arsonist who encourages bigotry and xenophobia to rouse his base". The former Trump booster added: "I'm a conservative". He's reckless on fiscal issues; he's incompetent on the border; he's clueless on trade; he misunderstands executive power; and he subverts the rule of law. "Republicans are firmly behind the president and any effort to challenge him in a primary is bound to go absolutely nowhere", said Republican Party Chairwoman Ronna McDaniel. But there are far fewer Republicans attempting to deny Trump a second term.
Walsh, who publicly supported Trump in 2016, has been telegraphing the longshot bid against Trump for weeks.
Tour Championship: Fans injured by lightning strike at PGA Tour finale
Northern Ireland's Rory McIlroy was a shot off the pace on 11-under after going through the first five holes at one over par. Play in the tournament was suspended for the day after the lightning strike.
Trump's national approval ratings in polls of all voters remain mired in the low 40% range, but are twice that among Republican voters who continue to approve of his 2 1/2-year performance in office.
That's why I'm running for President, and that's why I need your help. It won't be easy, but bravery is never easy.
On Sunday, Walsh said he apologized for past divisive comments. "The country is sick of this guy's tantrum, he's a child".
"Today I'm declaring my candidacy for president of the United States because it's time to be fearless", Walsh said in the video. "And, and it's hard, but I think that helped create Trump, and I feel responsible for that". There's no doubt about that, the personal, ugly politics.
(55 photos) - Amath Dansokho: Une levée du corps pleine d'émotions
Amath Dansoko, qui fut ministre, député et maire de Kédougou, était l'une des figures légendaires de la gauche sénégalaise. Depuis 2012, il était conseiller spécial du président du Sénégal et également président d'honneur du PIT.
"On more than one occasion, I questioned Mr. Obama's truthfulness about his religion", Walsh wrote. "Let's be real, these are scary times".
Trump is not the first sitting American president to face a primary challenge. A president who sides with foreign dictators over our intelligence community. We're exhausted of a president who thinks he's above the law.
US President Donald Trump sits in the driver's seat of a semitrailer as he welcomes truckers and CEOs to the White House in Washington, DC, to discuss healthcare, March 23, 2017.
Dem Sen. Chris Murphy: '50-50' Chance of Gun Background Check Deal
Democrats meanwhile can not push legislation through Congress without the backing of Republicans, who control the Senate and the White House.