It's important to know that if you want to discuss this with the chair of a department where you're interviewing, or have an offer, you will have to bring it up yourself; it's illegal (at least in the U.S., or at least in the states I'm familiar with) for a university to ask you about your marital status. You'll find that most departments are eager to help to the extent they can, and that there's wide variation in what that extent is.
Update: Based on the comments below, let me add that some chairs don't know what the law is, or don't care; so it's clearly not universally true that you won't be asked about your spouse.
Maybe I'll also add that, if I remember right, I never brought up my spouse until I had an offer. The interview stage is when you're trying to convince them that you should work there; the post-offer stage is the reverse. The problem with bringing up spousal issues at the interview stage is that the department may start thinking "We're never going to find a job for her husband in post-Inca ethnography, so maybe we should make an offer to somebody we're more likely to get." I think this would be somewhat unethical, but then again so is illegally asking you about your marital status, and it's sometimes done.
So the difficult question: what to do if you don't want to talk about your two-body problem at the interview, and you're asked about it? On general "keep the tone light" grounds I would advise against saying "You are breaking the law." If you said, "I'd rather keep this just about me for the moment," I would be fine with it; but for the sake of honesty I should say I'd expect some chairs would find it weird.
Perhaps the best thing would be to concede that you have a spouse, and to say something about what field they're in, but to play down any sense of a two-body "problem." If the spouse is an academic (which I think is the situation in the posted question), I think it is totally OK to create the impression that a TT job for your spouse would be a big draw, but not a necessity. This allows the math department to get the ball rolling on an attempt to do a double hire, but reduces the risk that the department will find out there's no job for your spouse and give up on you, too.
Note that the advice above only applies if you're (illegally) asked about your spouse in the interview. If you choose to bring it up yourself, I think you should be totally upfront about what will be required to hire you. If you are deadset against considering anything other than a double TT offer (e.g. if you are already situated in a place where you have one TT and one non-TT offer) then you should go ahead and bring this up to avoid wasting anyone's time.