Thanks for your responses, everyone.
Jade is right--it takes an open-minded, pretty flexible person to pursue a relationship with someone who is already married, but because I am mono (really!) that means that I have an awful lot to sort out as I go along. Iíve thought about it after reading your comments and I think it comes down to choosing between a less than perfect relationship with someone I really care for, or trying my luck with the multitude of jerks out there. And, based on some of your comments, maybe Iím not giving my partner, or polyamory for that matter, enough credit. He might be capable of loving and emotionally supporting me as well as his wife, even if it is to a much lesser extent.
I wish I could talk to him about all this! But Iím clearly the "needier" person in the arrangement and thatís not how I want to come across. It would be great if he brought it up, but I donít think heíd want to confront any of this either. So, here I am in--trying to understand my place in a poly world.