Mitch McConnell ended the suspense early.

Senate Republicans had been signaling since the untimely death of Supreme Court Justice Antonin Scalia that President Obama would not be the one who chose his replacement on the Court. On Tuesday, McConnell made his obstructionist statement in the bluntest possible terms: "This nomination will be determined by whoever wins the presidency in the polls. I agree with the Judiciary Committee's recommendation that we not have hearings. In short, there will not be action taken." The straightforwardness of McConnell's statement makes it clear that we've entered a new era of the Supreme Court nomination process. And it's an era in which Supreme Court vacancies will often be difficult to fill.

Senate Republicans have tried to argue that, far from breaking new ground, their refusal to consider any possible Obama nominee in an election year is merely upholding a decades-long string of unbroken precedent. This is quite simply jiggery-pokery, to quote a term made famous by Scalia. There are seven 20th century examples of Supreme Court justices being confirmed in an election year, in some cases much closer to November than the current vacancy. When Lyndon Johnson's nomination of Abe Fortas as Chief Justice was filibustered to death in 1968, the arguments focused on the accusations of corruption that would later force Fortas to resign — Senate leaders did not argue that the president had no authority in principle to make a Supreme Court appointment in an election year.

But while the categorical blockade of Supreme Court appointments is unprecedented, it doesn't come out of the blue, either. The Supreme Court nomination process has changed as the parties have become more ideologically coherent. The stakes of this particular nomination are particularly high, because the new median vote on the Court will almost certainly either be somewhat more conservative or much more liberal than the current one, Anthony Kennedy.

The ideological cohesion of the parties also helps to explain why McConnell and the Senate Republicans have taken such an uncompromising stance. Why, some commentators have wondered, did the Republicans not try to get a more moderate nominee than Obama (or, perhaps more to the point, Hillary Clinton or Bernie Sanders) would be inclined to nominate?

Part of the explanation is that McConnell has generally preferred high-stakes gambles. He could have tried to make the Affordable Care Act more palatable to conservatives or simply go all-out to try to defeat it, and he did the latter. But perhaps a more important reason is simply that there's not really much Obama could offer Republicans that both parties would find mutually acceptable. Even a relative blank slate like D.C. Circuit Court judge Sri Srinivasan is more likely than not to be a reliable vote for the liberal faction of the Court.

This hasn't always been the case. The Court has been controlled for more than four decades by Republican nominees who were conservative in many respects but were liberal on certain key social issues like abortion and gay and lesbian rights. On the other hand, JFK nominated Byron White, who was liberal on issues like civil rights and national power but was very conservative on issues like civil liberties and reproductive freedom. These nominations weren't "mistakes" so much as they reflected diverse electoral coalitions. FDR nominated some of the most liberal Supreme Court justices in history as well as some Southern segregationists. This isn't because he was mistaken about the latter, but because both types of judges represented crucial Democratic constituencies.

In that kind of partisan context, finding nominees who would be acceptable to both the president and Senate was easier. Those days are gone.

President Obama has announced that he will go ahead with a nomination anyway, and this is appropriate. The Supreme Court has generally not been a major election issue. It's not clear if it will be in 2016 despite the fight over the president's nomination power, but the Democrats will certainly try to make the Senate's obstructionism an issue in tight Senate races in blue states, such as Kelly Ayotte in New Hampshire and Mark Kirk in Illinois. If the Democrats are able to recapture the Senate and the White House, they will almost certainly be able to get a justice confirmed, as would a Republican president and Senate.

What if we have divided government, most likely in the form of a Democratic president and a Republican Senate? The brutal truth is that the Constitution provides no way of resolving such a deadlock. It is constitutional for the Senate to simply refuse to fill a Supreme Court vacancy. And despite their language about the election resolving the issue of the Supreme Court, I wouldn't bet on Senate action in such a case. If the people fail to decide the issue in November, Antonin Scalia's spot on the Supreme Court may not be filled for a long time.