Is it OK to mention a two-body problem during a tenure-track interview, if getting the job would actually resolve the problem? I'm having an upcoming phone interview for a tenure-track position and I expect that I will be asked the usual "Why would you want to work here?" question. Apart from reasons relating to the research competency and culture of the university, a major reason for me would be that moving to that institution would essentially resolve an ongoing two body problem - not entirely, as my spouse is not working at said institution, but at a place close to it. 


  Is it fine to mention this during the interview? 


Currently I reside in Europe, whereas the institution is in the US. My reasoning is that telling them should make it clear that I would indeed be serious to move there.
There are really two ways people can take this:


"If we extend this person an offer, he will actually accept." This is what you are hoping for. This can be good, especially if you are "too good" for the place you are applying to, where people might wonder why exactly someone with better prospects would choose to apply at a lower rate institution. Then again, it can backfire - if the institution assumes you would accept their offer for unrelated reasons, they might be less generous in the package they offer (pay &amp; perks).
"So... he only applies here because of his spouse?" This would be bad, or at least suboptimal. People might wonder whether you are really committed to working there. If choosing between two candidates whose portfolios both match what the institution is looking for, people might lean more towards someone who doesn't "need" his spouse working close by to apply.


I subjectively believe people will more often have reaction 1 than 2. So this argues for disclosing your motivation. Then again, note how this can reduce your possibilities in negotiation.

To be honest, I'd try to wow people with your experience, portfolio and all-around wonderfulness and keep this aspect below wraps. Unless people ask point-blank: "Would you really relocate from Europe to the US?" But that would likely come up later in the application process than in the initial remote interview.

I looked through Workplace but didn't find anything related. You may want to think about flagging your question for migration there - after all, similar considerations would also pop up for non-academic job seekers.