what do they have to gain from not using it?
It's not "what do you have to gain by
not using it" it's "what do you gain by using it," and the answer is
nothing. You gain nothing by using it. And what do you lose? Everything, any semblance of power that a minority party has in senate (which is a lot -- the senate is not the house) is lost; you lose any ability to force compromise on conservative house bills that come over to the senate for
at least 22 more months but probably 46 more months. Trump appoints another justice who is
more conservative and has less judicial prudence and experience than Gorsuch,
and McConnell dissolves the fillibuster as Trump and the House set to move on a tax plan and any other conservative legislation.
What else do they stand to lose? The structure of the senate. The ability for a minority party to have a legislative voice in the senate. Democrats are unlikely to gain a senate majority in 2 years, they have too many seats up to be lost in red states, and not enough to gain in blue states.
So many partisans are so short sighted on this and forget that Senators actually have to pass legislation, not just have political fights. "Well you prevented us from getting our guy so we're gonna prevent you from getting your guy!" And they think, "Well now it's even." Sure, now it's even in this baby size childlike mentality of tit for tat, but in the real world
Republicans lost nothing from stonewalling Obama's nominee and they effectively
gained a Supreme Court pick that they shouldn't have had. Republicans had
a lot to gain and legitimately had nothing to lose a year ago when Obama nominated Merrick Garland (a nominee who many Republicans would have been fine with if he was on the bench too) because they controlled the House and Senate and likely would still control the house and senate after November, and they could go on the gamble that some slim chance of them winning the White House... which of course, they did.
Democrats have nothing to gain and much more to lose. So many people are looking at losing the fillibuster and thinking "well it's not like Trumps agenda wouldn't pass eventually." This is true, but it's brain-dead stupid. The point of the 60-seat majority in the Senate is that it forges compromise on bills. There's a reason why Trump's health care proposals would have been killed in the senate, because building a 60-seat majority to pass that would have been impossible. It was that
requirement for compromise that ended up getting the Freedom Caucus in the house to kill the bill before it even came to a vote: THe compromises required on that bill for it to pass the senate made the bill not acceptable to far-right conservatives in the house. Without that need for compromise in the senate, it becomes much easier for the house to not consider compromise on bills and just send conservative bills over to the senate, which they can then pass with a 52-48 majority, and then it goes to King Trump and he signs it.
There's no brightside for Democrats on this. Saying that McConnell would have killed the fillibuster once it got to the next nominee is a stupid argument because you also lose all of that legislative compromise between now and whenever the next nominee comes along. Further, when the next Supreme Court nominee comes along from Trump there wouldn't have to be any effort to come up with a nominee with any judicial credibility (which Gorsuch
has, which is why many liberals and Democrats were relieved when Trump appointed Gorsuch ~2 months ago... We were all expecting the Betsy Devos of nominees, no experience, extremely far right, beholden to special interests, beholden to Trump Inc., and... Gorsuch wasn't, and then Gorsuch even criticized the President days later). The next nominee can be whoever Trump wants.
Republicans actually had something to gain in opposing Garland, as wrong as it was. Democrats have nothing to gain, and everything to lose.
My fellow liberals, though, don't want to hear this. They want to stick their fingers in their ears and scream "They did it to us we should do it to them!!!"
There is nothing to be gained from supporting Gorsuch. Quite the opposite.
You're not "supporting" Gorsuch. You still vote against him. I think in this hyper-partisan ideological purity death match people think that
not obstructing the legislative process means
endorsing conservative agenda. It doesn't. You can still vote against him.