The Democrats can delay, but they cannot prevent a hearing on the nominee in committee, although they can stop a final vote.  I suspect if the nominee is like Roberts, they wont. If he is plainly like Scalia, no vote will ever occur.  Such a nominee would be cannon fodder for a more acceptable pick. Of course, the other possibility is the GOP rejecting someone who does not seem pro-life enough, like they did with Harriet Miers, but that is not likely either.

It is not abortion rights that are as essential as the right to be left alone by reactionary legislative majorities. This is the bedrock of natural rights democracy. Sadly, the trend is that both conservative and liberal jurisits accept this while also accepting the kind of laissez faire capitalism condemned in the recent conferences on Erroneous Autonomy. That gave us a huge body of law that sticks it to the little guy.