Anyone who claims to know what will happen regarding the balance of power on Capitol Hill on Nov. 6 is guessing. This midterm election is a volatile mess.
Experienced analysts generally think the Democrats have the wind at their back and the benefit of history. This is true.
First, Democratic enthusiasm is consistently high. Second, with only two exceptions, every first midterm election in the last 100 years has gone against the party in control of the White House.
But the range of factors that will determine control of Congress are broader than these two things.
Let us begin with the math.