New Delhi, Nov. 2 -- Polls show Republicans facing a rout in the midterm elections on Tuesday. Some investors are nervous about another possibility: What if the election outcome isn't immediately known?

History shows investors don't have much to worry about. Right now, it doesn't look like the election will be particularly close.

On Friday, election forecaster Silver Bulletin gave Democrats a near-78% chance of winning control of the Senate and a 95% chance of gaining control of the House. In its simulations, Democrats on average ended up with 53 senators and 240 congressmen, well above the 51 seats and 218 seats, respectively, needed to control the Senate and House. But in nearly 20% of simulations, the Senate broke down either 51-49 i...