Opening night tickets?

Even though opening night tickets aren’t sold online (as far as I know), does that mean there are none available? What are the odds, if any, of getting a ticket if you go directly to the box office the day of an opening?

Specifically I'm talking about Hillary and Clinton. It's not out of any particular desire to go on opening night (though it seems cool; I never have) but because tomorrow is the last slot I have open for a show over the next few days.

If you're nearby then it's worth stopping by to check in the afternoon. By this point the guest lists should be pretty well set, so if there is anything available they would know by now. The worst they can say is "sorry, nothing is for sale."