It was a reminder of just how unprincipled Republicans have been in refusing to bring the court up to strength. This fight has been all about partisan advantage, and if that means the court must leave some important issues unresolved because of a 4-4 deadlock, so be it.
McCain's outrageous threat also highlighted a longer-term problem: the bipartisan repudiation of the idea that the Senate should defer to a president's choice of a Supreme Court justice so long as the nominee is well qualified, untarnished by accusations of personal wrongdoing and within the mainstream of legal thought.
In 2005, 22 Democratic senators voted against the confirmation of Chief Justice
And now McCain threatens to oppose "any" Hillary Clinton nominee – though his spokeswoman later said that he would "thoroughly examine the record of any Supreme Court nominee put before the Senate and vote for or against that individual based on their qualifications."
The Constitution does provide for a role for the Senate in the appointment of judges, including Supreme Court justices. But senators abuse that authority when they reflexively reject or block a nominee from a president of the opposite party. Merrick Garland, an experienced federal appeals court judge who was nominated by Obama in March to replace Scalia, still hasn't been afforded even a hearing.
If Clinton wins and the voters also install a Democratic majority in the Senate, Republicans who decide to stonewall her Supreme Court nominations may find that their ultimate check on the president — the filibuster — will be taken away from them. Democrats went part of the way there in 2013, barring filibusters on other presidential nominations after Republicans blocked Obama's appointments to an important federal appeals court.
The Republicans' obstructionism is wrong; it also could backfire by giving the next president an even freer hand in shaping the Supreme Court. Some might call that poetic justice.