I can understand why Democrats are so upset that Merrick Garland’s nomination for the Supreme Court never obtained a hearing or a vote. Although the Democrats had used the same tactic for lower court nominees, and although they had announced their intention to do it for any Supreme Court nominees as well, the Democrats never had the opportunity to follow through on their pledge. Thus, the Republicans were the first ever to deny even a hearing to a Supreme Court nomination. In so doing, they broke an important rule of US politics: The rules and practices of the Senate shall be altered only by Democrats.
It was the Democrats who first added the cloture rule to allow filibusters to be broken by two-thirds majority. Decades later, when Democrats had 61 seats, they reduced the cloture requirement from 67 to 60 votes. In 2005, the Republicans considered abolishing the filibuster for judicial appointments, but eventually backed off the idea. Eight years later, it was the Democrats, then in control, who followed through on the scheme, abolishing the filibuster for nearly all presidential appointments. (They made an exception for Supreme Court appointments, as they currently had none pending.)
It was the Democrats who first brought hyper-partisanship to the consideration of judicial appointments with their shameful treatment of Robert Bork in 1987. The waging of character assassination against an appointment to public office soon came to be known as “borking.” During the Bush administration, Democrats first made filibusters of judicial appointments standard practice.
The tactic of leaving a judicial appointment to languish without so much as a hearing was first used by Democrats in 1988, who hoped in vain that a Democrat might be elected when Reagan’s term expired. The tactic worked better when Democrats used it again in 1992 against Bush (Senior). In 2007, Democrats took the tactic to the next level, leaving several Bush (Junior) appointments to languish for the entire 110th Congress, a full two years without so much as a hearing. In 1992, Joe Biden (then chairman of the Senate Judiciary Committee) pledged to do the same for any Supreme Court nomination, but the occasion to do so never presented itself. In 2007, Chuck Schumer (now Senate Democratic leader) made a similar pledge, but again the occasion did not present itself.
In 2016 the occasion finally did present itself, but the parties were reversed. Republicans took the Democrats’ lower-court tactic and applied it for the first time to the Supreme Court. Democrats were outraged, having grown accustomed to a pleasant situation (for them) in which Republicans felt bound by tradition, but Democrats did not. For the first time, it was the Democrats who felt the sting of having the Senate’s practices being changed to their disadvantage.
I can understand why they didn’t like it.