No, they would be "discouraged voters" withdrawing from the process to show their disgust. Remember how the national media talks of "discouraged workers" who are no longer reflected in unemployment statistics. Real Terri supporters may well walk out in the 2006 and 2008 elections. This horror will not be forgotten or ignored as was, say, McCain-Feingold.
Doesn't anyone remember 1992? Bush 41 wasn't a conservative at all, but he still would have been better than what we wound up with. Disappointing as the Republicans have been, the Democrats would be a thousand times worse. (I live in a blue state, and I know). It makes much more sense to keep working to push the Republican party to the right than to try to form a third party, and hand victory to the left. Don't forget that W and the Repubs in Congress achieved a ban on partial-birth abortion (it's not their fault the courts overturned it). They need our support---and if right now they are faltering, then they need us even more---we have to stiffen their spines and keep them on the right track. It is folly to write off all the good Jeb and W have done because in this one instance, they dashed our expectations.