One hundred years ago this June, Supreme Court Justice Charles Evans Hughes resigned his position to accept the Republican Party nomination to the presidency. That left a vacancy on the bench only a few short months before a new president was to be elected. Woodrow Wilson put forward John Clarke of Ohio that July, and he was confirmed by the Senate just over a week later. Done and done.

With the death of Antonin Scalia this weekend, though, we seem to be headed for a much-rockier transition. Senate Majority Leader Mitch McConnell (R-Ky.) said in a statement that Scalia's seat "should not be filled until we have a new president" -- an unusual declaration that the body responsible for confirming Supreme Court appointments wouldn't act.

Part of this is certainly the timing of Scalia's death. The election is still nearly nine months away, but we're very much in the thick of it. What's more, since 1900, it's been very rare that a vacancy should arise this soon before a presidential election. (In large part, that's because during the past century vacancies have mostly arisen from carefully planned resignations.)

There have been confirmations that occurred closer to elections, of course (since the chart above shows only the point at which the Senate received the nominee). In 1988, for example, Anthony Kennedy was confirmed by the Senate on Feb. 3.

Layered on top of the infrequency of election-year appointments is the polarization of the Senate itself. According to scores calculated by Keith Poole of the University of Georgia, the Senate is more polarized today than it has been at any point on record.

That said, tension over a Supreme Court pick in an election year is not unprecedented. The chart above shows only the successful nominations, and so it doesn't include what happened in 1968.

As a report from the Congressional Research Service explains, a similar situation arose that year when Lyndon Johnson nominated Abe Fortas to fill Earl Warren's position as chief justice. Fortas's nomination was blocked by Senate Republicans looking forward to the November elections and some Democrats worried about his having taken speaking fees from business interests.

The Fortas nomination prompted the creation of an informal rule discouraging lame-duck appointments from sitting presidents. Fortas didn't get the gig, and Warren hung on until 1969 when he was replaced by Warren Burger.

If McConnell's threat holds, the Court could have only eight justices until some time after Jan. 20, 2017 -- at which point, we'll note, Democrats may very well control the chamber. But that wouldn't be the longest period during which the Court has remained incomplete.

The longest vacancy in court history, as the book "American Political Leaders" notes, was in the 1840s, when a seat was vacant for two years, three months and 18 days. Why? Because supporters of Sen. Henry Clay thought that he could win the 1844 presidential election and get the right to nominate his own justice. Clay lost, and James K. Polk filled the seat.

A few years later, there was another vacancy of over two years. That one followed a death shortly before a presidential election at another tense moment. In May 1860, Justice Peter Daniel died. By the time he was replaced, the country was in the middle of the Civil War.