Eight is enough? Photo: Evan Vucci/AFP/Getty Images

Senate Republicans have formed a united front around the principle Barack Obama should not be able to appoint a replacement for Antonin Scalia, and that the seat should instead be selected by the winner of the 2016 election. This “principle” rests on a wildly selective reading of senatorial history, according to which it is somehow improper for a president to fill a Supreme Court seat in his final year. In reality, this principle has never existed before and was concocted on the fly in order to justify the simple exertion of power.

The implication of this claim, though, is that if Hillary Clinton wins the election, Republicans will give her latitude to appoint a reasonably well-qualified, non-extreme jurist to the vacant spot. I have long been skeptical that Republicans would actually go along with this if it comes to pass. And now John McCain confirms it. In an interview touting fellow Republican Senator Pat Toomey, McCain pledges that he and his party will continue the Supreme Court blockade throughout Clinton’s term. “I promise you that we will be united against any Supreme Court nominee that Hillary Clinton, if she were president, would put up,” McCain said. “I promise you. This is where we need the majority and Pat Toomey is probably as articulate and effective on the floor of the Senate as anyone I have encountered.”

If Clinton wins and Democrats pull enough Senate seats, Republicans will oppose her nominee, and then, eventually, Democrats will change the rules to abolish filibusters of Supreme Court nominees. (Republicans will decry this foul measure and justify any subsequent actions of their own as justified revenge.) If Clinton wins and Republicans hold on to 51 seats, they will simply refuse to let any nominee through. The fact that it is McCain, a personal friend of Clinton and as strong an institutionalist as can be found in the Senate, who is proposing to extend the blockade indefinitely shows just how deep the commitment runs through the party.

The old norms held that presidents were given some deference in filling Supreme Court vacancies. Senators might object to a particular nominee on the basis of ideological extremism or lack of qualifications, but the president’s general right to appoint a member of his judicial team was considered sacrosanct. Like all the other norms holding back the exercise of power, this one has now collapsed. The new rule is that a president needs 50 senators to fill a Supreme Court vacancy.