That statement may be somewhat less on-the-mark than you think, given the many 5-4 decisions on some rather important issues that we've seen from the Rehnquist court.
since OConnor voted for one TEN Commandment monument and against another on the same day you make a good point. Since OConnor did not vote for Kelo then it looks like her vote is not a swing vote on ALL cases. Remember that Scalia voted to allow the flag to be burned.