To answer your question, I'll refer to a story about Reagan and Eugene McCarthy. When Reagan was running for president in 1980, Eugene McCarthy came out and supported him for president. People we surprised that a Democrat like McCarthy would support Reagan. McCarthy replied that he was supporting Reagan because "he was only candidate who understood the difference between being President and the Presidency."
Presidents need to be grounded in the human condition. One of the reasons that Reagan was a great president was that he never forgot that. I always felt that he was happy to be President, worked hard, did his best, and would be just as happy to leave the job as to keep it.
I distrust a candidate who's be-all and end-all is politics. Politics is a necessity of course, but if that is your focus and the only thing you live for, I don't want you anywhere near the Whitehouse.
Becoming the Pope is along the same vein - the more the individual craves the position, the less deserving they are of the office. Humility and a desire to serve with integrity have to be the main desire and focus.