The Catholic bishops have come out quite strongly against abortion pushing back against the Democrats who want to minimize this issue and make it a matter of personal choice. They are quite clear that the teaching of the church is settled on this issue and that Catholics cannot support pro-abortion candidates.
Bishop Gracida created an ad (to be used by Catholics to buy ads on their local radio stations) that makes it clear that a Catholic must vote their conscience, they cannot vote for a pro-abortion candidate and Obama is a pro-abortion candidate. He couldn’t be any clearer, don’t vote for Obama.

It will be interesting to see the results of this struggle in the exit polls. During the primaries Obama had a problem with Catholics but I’m not sure where he stands with them now. In the IBD shows a swing by Catholics to McCain, so who knows? The bishops may be having an impact on their flock.
In 2004 Kerry, a Catholic, lost the Catholic vote to Bush over the abortion issue but this year you have Catholics like Kmiec endorsing Obama as a pro-life candidate (when I saw that site I immediately thought of Isaiah 5:30). So, I think the issue is far from settled even though Obama is the most pro-abortion candidate that has ever run for president. That doesn’t seem to bother his Catholic and Evangelical voters, their conscience appears to be clear.