Here are five and Kerry would make six (orig. source):
Bill Clinton campaigns with doomed California Governor Grey Davis, 2003.
Bill Clinton campaigns with Vice President Al Gore, who lost the 2000 presidential election
Here's Bill Clinton with Walter Mondale, who spectacularly lost Paul Wellstone's Senate seat in 2002
Bill Clinton in Florida with Democrat gubernatorial cadidate Bill McBride, who beat out former Clinton Attorney General Janet Reno [corrected] for the nomination, but then lost the election to Jeb Bush in 2002.
Bill Clinton campaigns with Kathleen Kennedy Townsend as she runs for governor of Maryland, a heavily Democrat state, but she ends up losing the election to Republican Bob Ehrlich [corrected].
Another political campaign that went down with the Bill Clinton Curse was the Democratic ticket for the 2002 Hawaii gubernatorial race, Mazie Hirono and Matt Matsunaga. (I assume this is one of the 7.)
Slick Willie came out here to "save" the ticket and "revitalize" the Party. He mainly brought back memories of how slimy the Dems are. The Republican, Linda Lingle, won in a landslide.
This is in a state that is traditionally heavily Democratic.
Link: http://the.honoluluadvertiser.com/article/2002/Oct/31/ln/ln01a.html