Senator John McCain's political opponent called on him to step down following his brain cancer diagnosis. Kelli Ward urged McCain to step down so that she could take his place. "When the time comes that Senator McCain can no longer perform his duties in the Senate at full capacity, he owes it to the people of Arizona to step aside," Ward. If McCain were to step down, Arizona Gov. Doug Ducey would have to appoint a replacement until the 2018 midterm election.