Democrats:
January 3, 2008 – Barack Obama (38%), John Edwards (30%), Hillary Clinton (29%), Bill Richardson (2%), Joe Biden (1%)[17]
January 19, 2004 – John Kerry (38%), John Edwards (32%), Howard Dean (18%), Dick Gephardt (11%), and Dennis Kucinich (1%)
January 24, 2000 – Al Gore (63%) and Bill Bradley (37%)
February 12, 1996 – Bill Clinton (98%), "Uncommitted" (1%), Ralph Nader (1%)
February 10, 1992 – Tom Harkin (76%), "Uncommitted" (12%), Paul Tsongas (4%), Bill Clinton (3%), Bob
Kerrey (2%), and Jerry Brown (2%)
February 8, 1988 – Dick Gephardt (31%), Paul Simon (27%), Michael Dukakis (22%), and Bruce Babbitt (6%)
February 20, 1984 – Walter Mondale (49%), Gary Hart (17%), George McGovern (10%), Alan Cranston (7%),
John Glenn (4%), Reubin Askew (3%), and Jesse Jackson (2%)
January 21, 1980 – Jimmy Carter (59%) and Ted Kennedy (31%)
January 19, 1976 – "Uncommitted" (37%), Jimmy Carter (28%) Birch Bayh (13%), Fred R. Harris (10%), Morris Udall (6%), Sargent Shriver (3%), and Henry M. Jackson (1%)
January 24, 1972 – "Uncommitted" (36%), Edmund Muskie (36%), George McGovern (23%), Hubert Humphrey (2%), Eugene McCarthy (1%), Shirley Chisholm (1%), and Henry M. Jackson (1%)[18]
Republicans:
2008 – Mike Huckabee (34%), Mitt Romney (25%), Fred Thompson (13%), John McCain (13%), Ron Paul (10%), Rudy Giuliani (4%), and Duncan Hunter (1%)
2004 – George W. Bush (unopposed)
2000 – George W. Bush (41%), Steve Forbes (31%), Alan Keyes (14%), Gary Bauer (9%), John McCain (5%), and Orrin Hatch (1%)
1996 – Bob Dole (26%), Pat Buchanan (23%), Lamar Alexander (18%), Steve Forbes (10%), Phil Gramm (9%), Alan Keyes (7%), Richard Lugar (4%), and Morry Taylor (1%)
1992 – George H. W. Bush (unopposed)
1988 – Bob Dole (37%), Pat Robertson (25%), George H. W. Bush (19%), Jack Kemp (11%), and Pete DuPont (7%)
1984 – Ronald Reagan (unopposed)
1980 – George H. W. Bush (32%), Ronald Reagan (30%), Howard Baker (15%), John Connally (9%), Phil Crane (7%), John B. Anderson (4%), and Bob Dole (2%)
1976 – Gerald Ford and Ronald Reagan