Alexandria Ocasio-Cortez and Bernie Sanders are ideological allies, but it seems they disagree on how to convince voters to join them.

Sanders’s campaign has been growing more and more frustrated with the New York representative, who endorsed Sanders back in October, lending her political stardom to his presidential bid while he recovered from a heart attack. While the Vermont senator was stuck in Washington, D.C., for the Senate’s impeachment trial, Ocasio-Cortez campaigned on his behalf in Iowa.