Follow the money.
Since you make that accusation against longtime pro-lifers who are endorsing Romney, one could likewise say "Follow the money" in regard to what you are doing. You have a vested financial interest (I assume you accept donations) in drawing supporters away from Romney and to your candidacy.
Now I am not saying you are doing what you're doing for the money, but then I don't think you should say committed pro-lifers are endorsing Romney because of money.