I also think, though, cynically, that the GOP knows that "delivering" on the abortion issue would spell their doom and thus they won't ever do it.
I have thought that this holds for the Democrats and universal health care. They are better off having the issue "out there" than passing a bill. Of course, one could argue that the people would be forever grateful for universal health care if it passed. But I think that any health care system is likely to prove disappointing in some respects, so taking responsibility for it has a large down side.
Incidentally, I see education the same way. Conservatives and Republicans are probably better off having the voucher issue "out there" than having vouchers enacted. I don't think that vouchers can produce an educational miracle. My guess is that what a full-on voucher system could produce, at best, is approximately the same level of educational results at much lower spending.