Walsh publicly rescinded his support for Donald Trump in July 2018 after the Helsinki Summit between Trump and President of Russia Vladimir Putin. Walsh stated "I will never support Trump again," calling him "a danger to this country." Walsh was one of the few Republican supporters of the Special Counsel investigation conducted by Robert Mueller to determine the presence of Russian interference in the 2016 United States elections and possible collusion between the Trump campaign and Russian officials. Shortly before announcing his presidential campaign, Walsh stated in an interview with CNN's Brooke Baldwin "I don't know how anybody can read this report and think, 'This is behavior that we want in our president...'Criminal behavior, who knows? But, boy, dishonest, immoral, unethical? Heck yes it is. And I’ll tell you, Brooke, every Republican on Capitol Hill agrees with what I just said. They can’t say that publicly." Walsh had begun discussing the need for a conservative to challenge Trump in 2020 as early as December 2018 and began to discuss the potential for his own run early in the summer of 2019.