Thanks to Steve Harrelson's Under the Dome blog for mentioning this Washington Post story on the roles and importance of the spouses of presidential candidates. It mentions polls that show marital relationships and the spouses themselves influence voters to at least some degree.
Janet Huckabee is mentioned.
Janet Huckabee, whose husband, Mike, is trying to lay claim to the Christian right, is an executive with Red Cross and ran for secretary of state in Arkansas. Yet in an interview, she is careful to play down her influence and role. "I primarily support my husband," says Huckabee, who said she has kept her job for income, and travels on weekends with the campaign. "On a very simplistic level, I try to be a helpmate.
"My husband is the candidate. He doesn't need me to be as well."