There’s something odd about the state of Brett M. Kavanaugh’s nomination to serve on the Supreme Court. If you take The Washington Post’s whip count — that is, our assessment of how senators intend to vote on Kavanaugh’s confirmation — and overlay ideology onto it, the undecided senators are closer to the middle than the rest of their caucuses.

On the right, more conservative side of the Democratic caucus are Sens. Heidi Heitkamp (N.D.) and Joe Manchin III (W.Va.) respectively, undecided of their votes and hovering near the ideological middle. On the left, more liberal side of the Republican caucus are Sens. Susan Collins (Maine) and Lisa Murkowski (Alaska), similarly undecided and similarly more moderate.

But then, almost all the way to the right, another undecided senator: Sen. Jeff Flake (R-Ariz.). Flake is the primary reason that Kavanaugh’s vote is still outstanding, having pushed for a supplementary investigation by the FBI into allegations that, among other things, Kavanaugh assaulted a woman in high school.


(Philip Bump/The Washington Post)

(Higher bars indicate more senators in the same ideological range. Data on ideology is from VoteView.)

Both the distribution of votes and Flake’s position as an undecided outlier demonstrate how Supreme Court voting has shifted in recent years.

Compare the Kavanaugh whip count with that of the man he seeks to replace, former justice Anthony M. Kennedy. Kennedy was nominated by Ronald Reagan in 1988 and received overwhelming support. It was a time when presidential nominees to the court were often granted a leeway that today would be unthinkable.


(Philip Bump/The Washington Post)

Two years later, George H.W. Bush nominated David Souter to the bench. He, too, received broad support — except from the more liberal Democrats. Souter went on to be far more moderate than expected.


(Philip Bump/The Washington Post)

In 1991, the Senate considered the nomination of Clarence Thomas. Thomas, like Kavanaugh, faced allegations of inappropriate behavior and participated in additional hearings meant to consider the issue. His nomination was close, with most of the more liberal Democrats rejecting him — but enough supporting him for confirmation.


(Philip Bump/The Washington Post)

Ruth Bader Ginsburg was nominated by Bill Clinton in 1993. She earned broad support, save for several more conservative members of the Republican caucus. By now you’ve noticed the trend: With the exception of the controversial nomination of Thomas, there was generally bipartisan support for nominees, save at the ideological extremes.


(Philip Bump/The Washington Post)

The nomination of Stephen G. Breyer in 1994 was a bit more contentious, but not by much. The Republicans who voted against him were more mixed into the caucus ideologically.


(Philip Bump/The Washington Post)

Then in 2005, George W. Bush nominated John G. Roberts Jr., first as an associate justice and then, with the death of William H. Rehnquist, as chief justice. He was confirmed by a wide margin but faced more significant opposition from the Democrats' left flank.


(Philip Bump/The Washington Post)

The nomination of Samuel A. Alito Jr. by Bush (to fill the spot for which Roberts was originally nominated) was much more contentious. A Republican-controlled Senate confirmed him to the bench, with nearly every Democrat voting against him. The issue wasn’t scandal; it was ideology. (Among those who testified in support of his nomination was Judge Maryanne Trump Barry, the current president’s sister.)


(Philip Bump/The Washington Post)

In 2009, Barack Obama nominated Sonia Sotomayor to serve on the court, and it was the Republicans' turn to offer ideological objections. She received more support than Alito, but that included only more moderate Republicans.


(Philip Bump/The Washington Post)

That pattern held with Elena Kagan, nominated by Obama in 2010. She received fewer votes than Sotomayor, including only five Republicans.


(Philip Bump/The Washington Post)

Those five included Sen. Lindsey O. Graham (R-S.C.) who has used his support of both Sotomayor and Kagan as an argument in the Kavanaugh hearings, suggesting that Democrats should put partisanship aside. But that ship left port a while ago.

Consider Trump’s first nominee, Neil M. Gorsuch. Three moderate Democrats backed him; no others did. Every Republican supported his nomination.


(Philip Bump/The Washington Post)

It was the fewest defections from the majority of either party’s caucus since Ginsburg.


(Philip Bump/The Washington Post)

So how does Kavanaugh compare to past nominees? Let’s compare him to the most commonly cited analogue: Clarence Thomas.


(Philip Bump/The Washington Post)

There are two central differences. The first is that there are more Republican senators now than there were in 1991, meaning that Thomas needed Democratic support that Kavanaugh doesn’t.

But second, and more obviously, the Republican caucus is much more ideologically conservative now than it was then, while the Democratic caucus (including the two independent senators) isn’t. VoteView assigns a numeric score for ideology. In 1991, the Democratic senators that voted on Thomas scored an average of -0.3, compared to a current average of -0.33. In 1991, the Republicans averaged a score of 0.33. The current average is 0.49.

The idea that’s reinforced is one of increased partisan polarization. That polarization is now seemingly baked into the Supreme Court nomination process, with nominees since Roberts essentially fighting to earn a handful of votes from members of the party opposing the president. In a split Senate, that polarization has left Kavanaugh on the edge of being rejected.

But it’s not all bad news. That polarization has also likely solidified support from the Republican caucus