The fact of the matter is that Sen. Clinton is claiming basically the entire eight years of the Clinton presidency as her own, except for the stuff that didn't work out, in which case she says she has nothing to do with it.
There is no doubt that Bill Clinton had faith in her and consulted with her on issues, in the same way that I would consult with Michelle, if there were issues. On the other hand, I don't think Michelle would claim that she is the best qualified person to be a United States Senator by virtue of me talking to her on occasion about the work I've done.
Given Clinton's coyness about what exactly her White House role was, this certainly seems an effective line of attack. I wonder, though, if invoking his own wife isn't going to strike a discordant note with some voters.
And then there's this: Whatever you think of her, Hillary was not your average first lady. She has reasons to be vague about her experience — but they mostly have to do with the general election. The Democratic base would love to find out that, say, Hillary had in fact shaped the administration's Bosnia policy. The reason she soft-pedals is because it drives a lot of middle American independents and Republicans bonkers that an unelected first lady would have had anywhere near that kind of power and influence.
It might come at the cost of her future prospects, but a little candor from Bill speaking directly to what Hillary's White House portfolio was could make Obama look silly in a hurry.