A question about the Supreme Court and "blatantly political" issues

Fz has a good post below on odd groupings on the Supreme Court. Since I'm no expert on the Supreme Court, maybe he could help me out. He notes that the Supremes tend to divide by partisan affiliation on "blatantly political" issues (like abortion and gay rights) and to form strange alliances on others. I have a couple of questions. First, what makes an issue "blatantly political"? Is it a well-known issue, a moral issue, or something else? Second, in what areas are we likely to see strange groupings in the future?