Originally a supporter of Donald Trump, Walsh evolved into a persistent critic of the president despite affirming support for many of his policies. Walsh supported Donald Trump's presidential candidacy, even though he did not believe Trump could win Illinois. After the election, Walsh condemned some of Trump's cabinet nominations for their connections to Goldman Sachs. Contrary to the opinions of many other conservatives, Walsh voiced support for and confidence in Robert Mueller and his Special Counsel investigation. In July 2018, Walsh rescinded his support for Trump after his Helsinki summit with Russian President Vladimir Putin, saying "I will never support Trump again" and calling him "a danger to this country." In October 2018, Walsh criticized Trump for making statements he thought promoted violence. In April 2019, Walsh called for a primary challenge to Trump for the 2020 presidential election, and he reiterated that call in August 2019. In July 2019, Walsh said that he is considering primarying Trump, as well as saying that Trump's "entire life is a lie". Walsh suggested using the Twenty-fifth Amendment to remove Trump from office. On January 31, 2020, Walsh stated he would support any of the Democratic Party presidential candidates over Trump in the general election.