The little of the Democratic National Convention that I've caught so far has been fairly mild. There are compelling reasons -- mostly McCain's failure to get serious about the budget deficit -- for people like me who traditionally vote Republican to think about voting Democratic this year. But the Supreme Court is not one of them, and Senator Clinton's remark that the Court is caught in a "right wing headlock" was ridiculous.
The Court has two solid voting blocs -- Roberts, Alito, Scalia, and Thomas on the right and Stevens, Ginsburg, Breyer, and Souter on the left -- with Kennedy often casting the deciding vote with either bloc of 5-4 decisions. I've been shocked at three of the recent opinions of the left-leaning justices: Kelo v. New London on eminent domain, District of Columbia v. Heller on the DC handgun ban, and Kennedy v. Louisiana on the death penalty in child rape cases.
Based on their age and health, I think Stevens and Ginsburg are very likely to retire during the next president's term. I think Obama would be under pressure to nominate justices at least as far to the left as the two who retired, particularly facing a Democratic majority in the Senate. I think I'd be much happier with the justices that would result from nomination by McCain and confirmation by the Democratic Senate.
As I said, there are reasons for Republicans to think about voting for Obama. What would happen to the balance on the Supreme Court is not one of them.