It's an election year. Candidate challenges are inevitable

One challenge has already been decided by a court (dismissed), and six candidates have withdrawn.  Per the AZSOS, 18 cases are pending (caveat: some of those cases may yet be consolidated and at least one involves a candidate who has withdrawn as the result of another case)

From the Arizona Secretary of State -

So far, the "biggest" name to withdraw is Christopher Ajluni, the No Labels candidate in CD1.  I expect that to change as the challenge process grinds on.