Filibuster

"Why doesn't Reid just make them filibuster, then?"

Because he can't.

Every few minutes or so, any Senator who has the floor can note the absence of a quorum-- even when there's obviously a quorum present -- and the rules technically afford the presiding officer no flexibility in determining whether it's necessary. Once a Senator suggests the absence of a quorum, the chair is obligated to conduct a quorum call [...] The roll can be called quickly or slowly, but it has to be called either until there is unanimous consent for suspending it, or until it's called all the way through and a quorum is either established or not. And if it's not, the Senate automatically adjourns for the day and the pending business remains unfinished.

What this means in effect is that a dedicated team of participants in the filibuster could take turns an hour or two at a time (or more if they chose) occupying the floor [...] And any time they got bored or tired or even just mischievous, they could suggest the absence of a quorum and then disappear, forcing the Democrats to produce 50 Senators or face automatic adjournment. The only rule about how often they can do that is that "some business" must transpire between quorum calls. So if they decided to do it every five minutes or so, Democrats would have to drag 50 Senators to the floor each time, while the Republicans could go take naps. Which means that a "real" filibuster kills the schedule of almost every single Democrat and commits them to sleeping in their offices for however long it goes on, while Republicans can share the duties among 41 of them, one or two at a time, working in shifts.

If breaking filibusters was easy, Bush wouldn't have worried about 'em for his Supreme Court nominees. Read the whole thing, yatta yatta. Bits and pieces elided to condense a long quote and to remove a bit of partisan rhetoric.

Removing the filibuster entirely is another kettle of fish, of course.