The person who could defeat him, likely with one hand tied behind his back, would be Shaddegg. I don’t think Shaddegg will take the chance of losing the primary and his congressional seat both, which leave JD. JD has mixed approval in AZ, which I fear McCain would mine deeply. I like JD and would vote for him... but McCain would bloody him over Abramhoff as well as the lobby money his wife received when he was in congress.
Shadegg won’t challenge McCain but it isn’t because of his House Seat. Remember, Shadegg announced his retirement and had to be talked back into running. He may not run at all in two years.
JD would not even come close in a primary. I like JD but he is a buffoon and he is history.