In Iowa, you can win when you lose, and lose when you win. Results in the caucuses don't matter so much as those in the expectations game so campaigns are lowering the bar. Here are past winners, official and otherwise.
1972
Senator George McGovern was an unknown, but campaign manager Gary Hart realized Iowa could win him notice. Ed Muskie got 35% of the vote, but McGovern won 22.6%--and a lot more coverage
1976
Playing off his anonymity, Jimmy Carter ran on the slogan "Jimmy Who?" He finished 10 points behind "Uncommitted" but gained national attention for beating a crowded field after months of campaigning
1984
The bar for former VP Walter Mondale was daunting. While he won an impressive 48.9%, Gary Hart's 16.5% got him second place over people like John Glenn and catapulted him to a win a week later in New Hampshire
1988
Bob Dole was from nearby Kansas, so the race was for second. When Pat Robertson mobilized an army of Christian conservatives to give him a six-point win over George Bush Sr., the Vice President was badly gored
2000
Even Bill Bradley's campaign was predicting an Al Gore win, but it didn't predict a 63%-35% walloping. Gore's team got out the vote, and his victory nipped Bradley's momentum in New Hampshire