IN 2012, John Roberts, America’s chief justice, angered conservatives when he formed a majority with his four liberal colleagues to save Obamacare from its first major legal attack. Three years on, in 2015, he did so again to uphold campaign-finance rules for judges. Later that spring, he and Justice Anthony Kennedy teamed up with the liberals to rebuff a second assault on Obamacare. On May 1st, the moderate side of Justice Roberts reappeared when he once again shuffled to the left to stand...