The man who wins today's election will probably appoint three supreme court justices. That means that the character of the court for the next twenty years is likely to be established today. If President Bush is re-elected, the court will selected by someone who
1) Has said that he will appoint judges who will overturn Roe v. Wade.
2) Has vigorously and successfully fought to reduce civil liberties.
3) Believes that there are far too many environmental protections in place.
In other words, it's likely that this election will decide whether abortion becomes illegal in many states, and possibly in the nation. (You're against abortion? I am too. I just don't think that sending police to intervene in horribly complicated intimate decisions usually makes things a lot better.)
The other two issues are the ones that seem most important to me, because they're the hardest to undo. It's rare to get civil liberties back once you've lost them. And it's even rarer to be able to really restore environments that have been ruined.
You can destroy a lot of habitat in twenty years.