I’ve followed politics in the USA since G.W. Bush was elected a second time in 2004. I had one question:
Why are so many Americans so stupid?
And why are Americans so close to a 50/50 split in so many elections.
Here’s one possible explanation. Many, MANY make a lot of money when American elections are close: lobbyists, consultants, media, broadcasters. They have incentive to try to keep it close.

Freakonomics audiocast:
Some say the Republicans and Democrats constitute a wildly successful industry that has colluded to kill off competition, stifle reform, and drive the country apart.