A) Reagan had an endearing -- almost mesmerizing -- quality about him. Gingrich couldn't be more opposite of that.
B) Despite his track record, Obama knows how to deliver a speech and rally both his drooling fanbase and the morons out there who don't know anything about his political track record when they report to the polls once -- and only once -- every four years. Jimmy Carter did not have that.
C) Consider the political intelligence of the American people then vs. now.
This ain't 1980 dude. You say "I don't see why they wouldn't do it again." I say because the situations -- both the personalities involved and the increasing stupidity of your typical everyday American -- are nothing alike.