Originally Posted by gomugirl1656
Is the relationship really over if he chooses her, is it a deal breaker? Say if he decided to come back to you, would you take him?
Are you prepared to be his "spare tire"? Do you think that the "leftovers" from his relationships with other people are enough to satisfy you? <--(not very "poly" of me to say that but I think you're dealing with a "serial monogamist" so "poly dogma" doesn't apply as far as I'm concerned) Do you want to set the expectation that he can fly by the seat of his pants and you get to suck it up and deal with it?
If the answer to any of these questions is "yes", then continue to be a doormat and you should be successful.