The U.S. Supreme Court justices — (first row, from left) Clarence Thomas, Antonin Scalia, Chief Justice John Roberts, Anthony Kennedy, Ruth Bader Ginsburg, (back row) Sonia Sotomayor, Stephen Breyer, Samuel Alito and Elena Kagan — pose at the Supreme Court in 2010.

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From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish.

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And I'm Melissa Block. Two big rulings from the Supreme Court this week seemed to turn the notion of a politicized court on its head. The court struck down much of Arizona's immigration law, SB 1070, but it upheld a key provision. Then the court essentially upheld the Affordable Care Act. Neither decision broke along the predictable partisan lines, five Republican appointees to four Democratic appointees, but that doesn't make the court any less of a political animal. NPR's Ari Shapiro looks at the politics of the court and why they matter.

ARI SHAPIRO, BYLINE: People often complain about activist courts, and that phrase is easy to define, says Professor Jeffrey Segal of Stony Brook University.

JEFFREY SEGAL: Activism is a decision that people don't like.

SHAPIRO: But a partisan court is a little different.

SEGAL: Political polarization means that, by and large, the center is disappearing.

SHAPIRO: There was a time when justices appointed by Democrats and Republicans intermingled in their judicial decisions. Ideological lines were murkier, and it was harder to predict who would fall where in a split decision. The last two justices who retired, David Souter and John Paul Stevens, were both Republican appointees who usually voted with the court's liberals.

But since they left, the court has settled into a partisan pattern of 5-to-4. That was troubling to Chief Justice John Roberts, who took office back in 2005, saying it was bad for the court and bad for the country when the justices issue high-profile decisions on 5-to-4 partisan grounds. Jeffrey Rosen is a law professor at George Washington University and a Roberts watcher.

JEFFREY ROSEN: He thought that it would just be a very serious loss if the court's legitimacy and trust by people who disagree with its decision were abandoned. It shows how seriously he takes the specter of polarization and how much he wants to avoid it.

SHAPIRO: Nonetheless, in more recent years, there have been several high-profile cases that split along the standard political divide, most notably the Citizens United decision striking down the nation's campaign finance laws and opening the floodgates to corporate money in elections. That's what makes this week so notable. Kannon Shanmugam is an attorney who clerked for Justice Antonin Scalia.

KANNON SHANMUGAM: In the two biggest decisions this week, there were majorities of the Supreme Court that consisted of both Democratic and Republican appointees. And so I think that it is grossly oversimplistic to say that all of the Republican appointees vote in one direction and all of the Democratic appointees vote in another.

SHAPIRO: In the ruling on Arizona's immigration law, Justices Anthony Kennedy and Chief Justice Roberts joined three of the more liberal justices to strike down parts of the law. And in the health care ruling yesterday, the chief created a five-vote majority to uphold the law by crossing the aisle again. At the same time, two of the court's liberal justices joined the conservative wing to limit the law's Medicaid expansion.

On Capitol Hill, Democratic Senator Chuck Schumer of New York sounded as surprised as he was pleased.

SENATOR CHUCK SCHUMER: This decision preserves not only the health care law but also the Supreme Court's position as an institution above politics.

SHAPIRO: That position is crucial to the court's standing, says Bert Brandenburg of the group called Justice at Stake, which bills itself as preserving impartiality in the courts.

BERT BRANDENBURG: There's another factor here which is, over the last 10 years, there has really arisen something of an industry that profits from attacking the courts no matter what they do. And this is a combination of pundits and commenters, for whom - it's ratings, and consultants, for whom it's - you can raise money off a decision you don't like, and politicians who harvest votes. So the courts are up against a lot.

SHAPIRO: All of that political pressure on the courts has taken a toll, says Karlyn Bowman of the American Enterprise Institute. She studied public approval of the Supreme Court.

KARLYN BOWMAN: In the year 2000, we were feeling pretty good about everything. The court was rated very highly. It's rated much less well on that hard measure of approval today.

SHAPIRO: In the late 1980s, court approval was as high as 66 percent. A New York Times poll from earlier this month puts court approval now at 44 percent, with three-quarters of respondents saying the justices decide cases based on their personal or political views. Still, that's far better than Congress, which has seen its approval rating fall as low as single digits this year. Ari Shapiro, NPR News, Washington. Transcript provided by NPR, Copyright NPR.