I would like to see the Democrats adopt a moderate pro-life stance on abortion, and with the ascendency of people like Harry Reid, that is becoming more of a reality. The Democrats are a much better home for Pro-Lifers than they were 10 years ago.
This is pointless - is it preferable to loose the votes of the 40% of the country that is pro-choice and gain a couple of precent of the religious vote? I think, and hope, that the Democratic party will be holding firm on abortion rights, simply because it makes electoral sense.
I don't think the Dems would lose all of the pro-choice voters. Assuming that the GOP was still pro-life, the pro-choice voters might stay home and not vote, but the great majority still would vote Democratic even if they weren't happy with the abortion position.
The reality is that those who are pro-life are much much more likely to refuse under any circumstances whatsoever to vote for a candidate who is pro-choice, even if that person agrees with them on every other issue. Those who are pro-choice are more willing to support a pro-life candidate as long as they like most of the rest of what they have to say.
So while the country is split down the middle, with actually slightly more people being pro-choice than pro-life, it is politically advantageous to be pro-life.
Gun control is another issue that fits this. About 70% of Americans oppose the NRA's position on gun control, and generally favor it, but there are very few people who are so pro-gun control that they would refuse to ever support an NRA backed candidate. There are lots of NRA members who would never under any circumstances whatsoever support a candidate who didn't have the NRA endorsement.
So again, most people are pro-gun control, but politically, it's better for a candidate to be anti-gun control.