I just found this January 29, 2007 Newsweek piece profiling Michelle Obama, another smart, powerful candidate's wife who has been portrayed positively. Though this article ends with these words: "In the past, Michelle has occasionally played tough enforcer with Barack in interviews but, as Nancy Reagan and Hillary Clinton can attest, voters prefer First Ladies who use a soft touch." So these women are media-savvy and obviously are constructing the image they want to project; they are playing the role of "spouse" or "help-mate" as women who are very invested and interested in their husband's political career (unlike Howard Dean's wife, whose disinterest in his political future seemed to doom the likelihood of his becoming the Democratic candidate) but who are not going to do a "Hillary" and try to get their own vision of national health care enacted if their husband becomes President.
It's interesting that Elizabeth Edwards retired from being an attorney in 1996 to administer the Wade Edwards Foundation, and now acts as a close political adviser to her husband--perhaps this is less threatening to women than Hillary Clinton, who was a working mother throughout Chelsea's childhood years, and whose ambition seems to disturb other women (and men). Judith Warner makes this point about Hillary in her blog in the New York Times this week.