It's always interesting to see how the Court aligns on issues like this one. In this case, Breyer wrote the decision and Ginsberg wrote the dissent. She was joined by Scalia and Kennedy, hardly her usual allies. Kennedy is usually depicted as the "median Justice" on most traditional left-right votes. He was decisive on Citizens United and may also be the swing vote when the Defense of Marriage Act comes up later this term. Thomas is usually attached at the hip to Scalia but voted in favor of the doctrine in this case.
While a unidimensional model of political conflict
explains a lot about American politics, there are some issues that do not fit that model and create unusual alignments like this one.