So the question is, Did the democrats filibuster the Alito nomination?Good question! I'll go through some evidence, and then comment generally.
The democrats want to argue that it is unprecedented to filibuster a Supreme Court nomination, but at least some of them voted against cloture in the Alito nomination. Generally, people don't consider that a filibuster because it didn't actually hold up the nomination.
Confirmation vote: 68-31. Cloture vote: None.
Confirmation vote: 58-42 (Dems, 4-41). Cloture vote: 72-25.
(Dems, 20-25, Harkin missed the vote; note that Obama was No-No).
Confirmation vote: 78-22 (Dems, 23-22). Cloture vote: None.
Confirmation vote: 87-9. Cloture vote: None.
Confirmation vote: 96-3. Cloture vote: None.
Confirmation vote: 52-48 (Dems, 11-46). Cloture vote: None.
What can we say about all of that? To filibuster is to insist that a bill or nomination needs 60 votes. On the easy confirmations -- Roberts, Breyer, Ginsburg -- we can't say much of anything. For all we know, the three Senators (or maybe one or two of the three Senators) who opposed Ginsburg were fully prepared to vote against cloture, but didn't see any point in forcing a cloture vote since there was no other opposition. The same is true even for the somewhat less easy confirmations, Roberts and Sotomayor. We can neither say that there wasn't, or that there was, a filibuster against those nominations. All we know is that a filibuster, if there was one, did not come to a vote.
On the tough ones, we can say something. First, it's clear that there was no filibuster against Clarence Thomas, even though 48 Senators, 46 of whom were Democrats, opposed the nomination. Clearly, if we think of them as a group, they did not consider opposition the same thing as filibustering.
On Alito, I think we can safely say that the 25 Democrats who voted against cloture (and probably a 26th, Harkin), including Barack Obama, were engaging in a filibuster. We can also safely say that the 16 Democrats who opposed the nomination but voted for cloture were not engaging in a filibuster. It's possible that their votes did not indicate their true positions...some of the 16 might have flipped to yes despite "really" engaging in a filibuster once they saw that they didn't have the votes; some of the 25 might "really" have been only registering protest votes, and would not have voted that way if the outcome was in doubt. But in general, I think it's fair to hold them to their votes. Whether it's fair to say that "the Democrats" used a filibuster to stop Alito is a harder call. On the one hand, many Democrats did filibuster. On the other hand, collectively the opponents of the nomination -- all but one of whom were Democrats -- had the votes to defeat cloture, but they did not do so.
But if you ask me what I think...
I think that on Roberts, the odds are good that the Democrats were split. At least some of those who opposed Roberts were carrying on a filibuster, but when it was clear that they didn't have the votes, they didn't press on to force a vote they would have lost. The evidence in general from that era suggests that many Democrats considered opposition and a filibuster to be the same thing, but others did not. So there was a bit of a filibuster on Roberts, most likely, with fewer than 20 participating. On Sotomayor, however, I think that there probably was more unanimity among her opponents that opposition equals filibuster, although for a variety of reasons the Republicans did not want to cast a losing vote against cloture, so they didn't force a vote. So I do think that there was a filibuster against Sotomayor, just as I think there is one now against the new nominee, whoever he or she turns out to be. The opponents (at least most of them) are going to insist on 60 votes, and that's a filibuster, regardless of whether anyone uses that word or winds up forcing a cloture vote.