Ernst's relationship with Steve King, a Republican House Representative known for his racist rhetoric and support for far-right politicians, has been criticized. In 2016, when King faced a primary challenge for his House seat, Ernst endorsed him, saying he "stands strong for life and liberty." In 2017, when King attracted criticism for saying "we can't restore our civilization with somebody else's babies" and for supporting European far-right politicians, Ernst said she did not condone King's behavior but would not ask for his resignation. In 2017, The Des Moines Register wrote a scathing editorial against King, which criticized Ernst for endorsing him in the past and not condemning him. In 2018, Ernst appeared with King at a rally in his district after King had endorsed a Canadian politician with neo-Nazi ties.
