In every election there's a certain group of people who choose their candidate based on his/her stance on abortion. Given the way the US Constitution was/is written a candidate's stance on abortion is about as pertinent as his/her musical tastes.
I found the following posting which states this point a bit more eloquently than I:
Candidate leadership on abortion. Ha..
The president has the power to appoint Supreme Court justices, that's the extent of his/her influence on the Court. The President has no power over the court's decisions once he/she has had their appointees approved by the senate and sworn in. Justices are generally in the court for life (like former Chief Justice Rehnquist) unless they choose to resign (former Justice Thurogood Marshall) or retire (former Justice Sandra Day O'Connor).
Even recent appointee, Justice Samuel Alito, has stated that regardless of his personal views on abortion his job is to uphold the laws of this country and as of now abortion in the first trimester is legal-- thus he will uphold said law unless a case comes before him which would challenge the precedent set by Roe vs. Wade (if you haven't already, read the above linked article to learn what would need to occur in order for that to happen).
So those who are crying foul of Sarah Palin because personally her view is Pro-Life and trying to scare people from voting for McCain/Palin are just as disingenous and flawed in their logic as those who refuse to vote for Obama/Biden because they happen to be Pro-Choice. They can no more ensure Roe vs. Wade will be upheld than McCain or Palin can ensure that it will be overturned. Therefore, the fact that Palin is Pro-Life is her opinion, she hasn't "forced" that opinion on anyone nor could she even if she wanted to. She has just as much right to her pro-life stance as any pro-choicer has a right to his/her opinion... And it will have little or no bearing on the job any of the candidates running for President will do once they are elected.
I'm not going to tell anyone who they should or shouldn't vote for. It's a very personal decision. People should vote for whomevever they feel will do the best job or whomever they feel "speaks for them." I just want people to be wary of the wiles of the politicians in each party and to make their decisions based on issues that the candidates can/will actually have an impact on. And abortion is not one of those issues.