If President Obama gets re-elected, he'll control the White House for the next four years - and the Supreme Court for the next twenty-five. The average tenure of a Supreme Court Justice today is 25 years, as Clint Bolick recently pointed out in the WSJ. Obama has already nominated two relatively young knee-jerk liberals to the Court (Kagan and Sotomayor for those keeping score at home). How many more justices will Obama get to nominate? Look at it this way: three justices - Scalia, Kennedy, and Ginsburg - will reach their 80s during the next presidential administration. And Stephen Breyer will be in his late 70s.
Bolick is right to remind us of the many 5-4 decisions in recent Supreme Court jurisprudence. Just one more liberal vote could undo any or all of these: campaign finance (Citizens United), gun rights (Heller and McDonald), school choice (Zelman). Even in the recent healthcare case, the positive aspects of the decision, setting limits on the Commerce Clause and on Congress's power to coerce states , attracted only five votes.
Now that John Roberts is officially a "swing vote," the need to get conservatives on the Court is more pressing than ever. A Romney presidency does not guarantee conservative justices, but another Obama term absolutely guarantees more liberal justices. For the left, it will be a gift that keeps on giving.