Supreme Court could be most liberal in decades

Expect a left turn in the Supreme Court in the coming months.

Even if Senate Republicans succeed in blocking President Barack Obama's expected nominee to replace Antonin Scalia, the court will likely be the most liberal in decades.

That's because nearly every justice — Democratic or Republican — has become more liberal over time. Even before the death of Scalia on Saturday, the justice in the ideological center of the court (in this case Justice Anthony Kennedy) was slightly more liberal than conservative, the first time that's happened since the 1960s.

Those findings are based on a prominent quantitative approach to measuring the views of the justices — Martin-Quinn scores. The model uses each justice's voting pattern in relation to the other justices to place him or her on a spectrum between liberal (more negative scores) and conservative (more positive scores). Justice Samuel Alito is the sole exception to the liberalizing of the court.

The data go to summer 2015, when the last term ended. Removing Scalia and assuming that the other justices didn't drift too far ideologically, then the court as a whole has a median score of -0.93. There hasn't been a court that liberal since 1939.

Of course, the actual decisions of the court are often determined by the real median justice — the swing vote who can break a tie between the eight other justices. With Scalia gone, the court is more likely to deadlock between the four liberal justices and the four moderate to conservative justices. In that case, the decision reverts to the lower courts' ruling. (It's been noted that Scalia's death could alter the outcome of a number of cases on the court's docket.)

Reverting to the lower courts is a winning scenario for Democrats, because two-thirds of Americans live within the jurisdictions of a liberal circuit courts, which are currently stacked with Democratic appointments. If liberal lower courts run right over the Republican-imposed stalemate in the Supreme Court, it may be better for conservative senators to accept a moderate proposal than stick to Senate Majority Leader Mitch McConnell's promise to block any nominee.

Still, Republicans seem set on stalling the process for as long as possible. It would be nothing new — taking extended time to make any action on Supreme Court nominees has become more common in recent decades, according to data from the U.S. Senate.

In fact, if the Senate delays the president's nomination by just 100 days, then Obama will have the highest average wait time in history between nominating a justice and getting a response from Congress. That would be if Obama nominates someone by the end of February and Congress decides in early June.

Currently, former President George H.W. Bush holds the record with an average of 84 days waiting. He had to wait 99 days for the approval of current Justice Clarence Thomas.

The current record for the longest time waiting on a single nominee was for Louis Brandeis, who was confirmed 125 days after Woodrow Wilson nominated him in 1916. Needless to say, if Republicans fail to respond to a nominee for the rest of Obama's term, that would be 329 days, far more than either record.

At some point, that may start to seem unreasonable. While Obama may not be able to push through a nominee as liberal as his previous choices —Justices Sonia Sotomayor and Elena Kagan — he may have success with a moderate. Even a justice like John Paul Stevens — a moderate when he was nominated by President Gerald Ford — had become the court's most liberal justice when he retired in 2010.

The question with a moderate justice is how he or she would fit in with the current court, which is made up of justices appointed by five presidents.

As could be expected with a court evenly split between the two sides, there's seldom clear consensus among the justices, especially on the conservative side.

The more liberal members of the court tend to decide cases together, according to data from SCOTUSblog. Justices Stephen Breyer and Ruth Bader Ginsburg agreed on 94 percent of cases in the 2014 term. On the other side, Thomas and Alito, the most conservative justices according to Martin-Quinn scores, agreed on only 81 percent of cases in that time.