In October 2019, Ruffalo tweeted that "until George W. Bush is brought to justice for the crimes of the Iraq War, (including American-led torture, Iraqi deaths & displacement, and the deep scars—emotional & otherwise—inflicted on our military that served his folly), we can’t even begin to talk about kindness." In November, while on "The Late Show with Stephen Colbert", Ruffalo endorsed Senator Bernie Sanders for president stating "you know when he gets in the office, he is going to be fighting for us". The same month, along with other public figures, Ruffalo signed a letter supporting Labour Party leader Jeremy Corbyn describing him as "a beacon of hope in the struggle against emergent far-right nationalism, xenophobia and racism in much of the democratic world" and endorsed him for in the 2019 UK general election.