Insider trading?

As of the time I'm writing this the Dow is up 293 points (3.15%).

Do stock traders have some inside information like early exit polls or something?

Or is this just another volatile day like the past 2 months

I think they already know who will win.

There haven't been many days lately where the Dow hasn't gone up or done a couple hundred points

Hedge fund traders.

Buy low; sell high

Does the market traditionally rise just after an incumbant is replaced? Maybe more with one party than the other, but generally a rise either way?

It'd make sense to be buying in the days coming up to an election if you are armed with that piece of information.

Of course, expect a sharp drop after the election if the candidate elected does not have the long term confidence of Wall Street, and they profit from the short term spike and run.