I did something similiar completely by accident. :)

The pope died and a vote was called. I tried to buy someone elses votes, it didnt work, I clicked the check mark and somehow managed to exit the vote screen. This left the papacy VACANT. I continued to not call a vote until I had more cardinals and could guarantee one of my guys would get in, primarily because I wanted a crusade....

So once the pope dies, you can avoid him coming back so long as you have one cardinal and avoid voting for a faction.