Both of us are currently 3+ year TT in different universities. We are in very different fields. We will apply for positions in the same university. Do we have to mention that I and my spouse are applying for two different positions (both TT positions) at the university in the cover letter?
If we mention, perhaps the departments can be more favorable for us, especially when it is in some isolated locations. But, at the same time, the departments could cross out us, because in this economy there are always likely enough good candidates; so why bother with dual career people?
If you get a married couple they are less likely to move again. OTOH if they think one of you will decline if the other doesn't get an offer and they aren't into spousal hires I guess it could be a negative and make them more reluctant to interview and make an offer.
There has been a lot of discussion though of if/when to raise the issue. This appears to depend on the culture and policies of the university in question. Some are keen on hiring couples and others are neutral or negative. Is it possible to ask someone there who is not on the search committees for some info on that?