It depends on the election. In primary elections, you can only vote for candidates from the party to which you belong. In general elections, you are free to vote for anyone you like, regardless of their party affiliation.

Beginning January 1, 2019, Iowa voters will be required to show a driver’s license, non-driver’s ID, passport, military ID, veterans ID, Tribal ID or Voter ID Card at the polls before they vote. Voters, starting in 2019, without an ID may cast a provisional ballot or have another registered voter attest to their identity.