If, by some cheat, he does "win" the election, it will be his VP choice that becomes president--if not before the inauguration, then certainly very shortly afterwards.
While searching for something suitable to post on this topic, read one commentary stating he “may last his first term”, but it was very, questionable.
Even shortly after means he’s president. We could have 46 and 47 in a very short time. Hopefully we stick with 45!