Would you get on a plane with a pilot who has never flown? Would you trust your child with someone who has never cared for children? Would you go under with a surgeon who has never operated?The job of President of the United States is unique. So by their logic, the only person qualified to be elected president is a former president.
By the way, given John McCain's history of crashing jets, using the pilot analogy is probably not a good idea.
HT to TPM...and Jimi Hendrix.