Buck has advantage in tight race

In the home stretch of tight political races, it gets harder to pick winners based on the polls. But the guessing is made a bit easier by what history tells us about the behavior of undecided voters, whose last-minute decisions can make all the difference.

Take the Senate race in Colorado, where Republican challenger Ken Buck either holds a slim lead or is in a dead heat, depending on the survey. The fact that he is neck-and-neck with an incumbent, Democratic Sen. Michael Bennet, actually is a reason for him to be optimistic, because of how undecided voters tend to break at the end.

Why? Simply put, the rule of thumb is that incumbents get relatively few of the votes from those who say they are undecided on the eve of an election. So incumbents trailing at this late stage are in trouble. But so are incumbents with small leads or who are dead even in polls that put them only in the mid-40% range.

The theory isn't absolute, however. Like all rules in politics, it comes with enough caveats to give pollsters cover.      –More-