Democrats: Since 1972, the Iowa caucus accurately picked the eventual nominee four times out of eight, for a 50% rating. 1992, in particular, saw Bill Clinton come in fourth behind Harkin, Tsongas and Uncommitted.
1972
Uncommitted: 35.8%
Edmund Muskie: 35.5%
George McGovern: 22.6%
Hubert Humphrey: 1.6%
Eugene McCarthy: 1.4%
Shirley Chisolm: 1.3%
Henry Jackson: 1.1%
1976
Uncommitted: 37.2%
Jimmy Carter: 27.6%
Birch Bayh: 13.2%
Fred Harris: 9.9%
Morris Udall: 6%
Sargent Shriver: 3.3%
Henry Jackson: 1.1%
1980
Jimmy Carter: 59.1%
Edward Kennedy: 31.2%
Uncommitted: 9.6%
1984
Walter Mondale: 48.9%
Gary Hart: 16.5%
George McGovern: 10.3%
Uncommitted: 9.4%
Alan Cranston: 7.4%
John Glenn: 3.5%
Reuben Askew: 2.5%
Jesse Jackson: 1.5%
Ernest Hollings: 0%
1988
Richard Gephardt: 31.3%
Paul Simon: 26.7%
Michael Dukakis: 22.2%
Jesse Jackson: 8.8%
Bruce Babbitt: 6.1%
Uncommitted: 4.5%
Gary Hart: .3%
Al Gore: 0%
1992
Tom Harkin: 76.4%
Uncommitted: 11.9%
Paul Tsongas: 4.1%
Bill Clinton: 2.8%
Bob Kerrey: 2.4%
Jerry Brown: 1.6%
1996
President Bill Clinton was unopposed for renomination.
2000
Al Gore: 63%
Bill Bradley: 35%
Uncommitted: 2%
=====
Republicans: Three times out of eight saw Iowa get it right. Note 1980. Note also that twice there were no caucuses because of incumbents running, so I guess that means Iowa got it right three times out of six.
1976
Gerald Ford: 264
Ronald Reagan: 248
Undecided: 62
1980
George Bush: 31.6%
Ronald Reagan: 29.5%
Howard Baker: 15.3%
John Connally: 9.3%
Phil Crane: 6.7%
John Anderson: 4.3%
No Preference: 1.7%
Robert Dole: 1.5%
1984
President Ronald Reagan was unopposed for renomination.
1988
Robert Dole: 37.4%
Pat Robertson: 24.6%
George Bush: 18.6%
Jack Kemp: 11.1%
Pete DuPont: 7.3%
No preference: .7%
Alexander Haig: .3%
1992
President George Bush was unopposed for renomination.
1996
Bob Dole: 26%
Pat Buchanan: 23%
Lamar Alexander: 17.6%
Steve Forbes: 10.1%
Phil Gramm: 9.3%
Alan Keyes: 7.4%
Richard Lugar: 3.7%
Maurice Taylor: 1.4%
No preference: .4%
Robert Dornan: .14%
2000
George W. Bush: 41%
Steve Forbes: 30%
Alan Keyes: 14%
Gary Bauer: 9%
John McCain: 5%
Orrin Hatch: 1%
http://desmoinesregister.com/extras/politics/caucus2004/pastresults.html=====
Sum total: Iowa gets it right half the time.