Dan, absolutely there's politickin going on in case selection. I saw that scenario discussed during the DOMA/Prop 8 stuff. I only saw the article once, and one of the actual lawyer/court fans will have to correct anything I misremember but:
They decide on their cases in a conference. I think it's actually called In Conference. And there are apparently RULES and rules for how they should vote for or against cert. And the reporter suggested one of the judges may have played a little fast and loose with the lower case rules when voting for Cert, and the Court may have to somehow reverse granting cert thought a process I don't remember the name of.
Again, this was all speculation on the part of the reporter, and whatever he thought was going to happen somehow didn't.
But it does answer the question that yes, there is some level of politicking going on as far as case selection- at the very least in so far as judges won't grant cert in a case they want to "win" if they aren't pretty sure they've got a shot at "winning" the decision. It's better to leave it reviewable, than grant cert and have to find a way to tap dance around stare decisis.