Hil, I don't your department or the people there, but this is what would happen in my university, which is more or less a twin of yours.

You would explain to the chair that you have been happy there and have been planning to stay, but that you had interviewed for another job with some attractive features and if they made you an offer in the next couple of weeks you would have a difficult decision to make. Depending on how much they value you, your chair would either say "Ok, tell me as soon as possible so I know whether I need to go to the trouble of finding someone else" or will ask you not to accept the other position until he/she can consider options that might help them to retain you.

If they really insist on an immediate decision (jerks!) I would tell them you are staying, because at the moment that is true. You have no other options. It is commonplace, for instance, that our lecturers will get a last minute offer for a visiting professor position at a smaller school that they think might turn into a tenure track line, and they have to back out of a contract with us. It doesn't upset anyone. They are our colleagues. We want them to get the career that they want. We try to find a way to make it worth their while to stay, but if they go we are happy for them.

Thanks, Rick.

I'm with Rick. My department is all NTT faculty, so we know that sometimes folks will sign a contract and then get a more attractive offer elsewhere.

I agree with Rick.

In addition to what Rick said, go forth, tell them you are staying, and try not to worry about it. In the end, you are trying to do what's best for you and it isn't your fault the other job is taking so long. You have interacted with them in good faith.

While, I clearly agree with Rick, it did not need to be asserted three times.

Hil, what Rick and le nubian said. In the end, you have to do what is best for you.

I know I should be grateful that Mom is making a quick run to the market for me while I am still so tired, but why does a trip to the grocery store for 3 items always require 3 phone calls?

Yay Rick for good advice. And per his advice, being a good person. ;)

Thanks for the advice, everyone.

One more day of class. And then final exam on Monday. And then not too much grading, and then entering grades, and then dealing with emails from students who don't like their grades, and then the semester is over.