Democrats may take the House but they shouldn't expect a mandate

There are a dozen or so House races that Democrats are all but guaranteed to win. About 30 additional House races could go either way. Democrats only need to win about a third of these races to take the majority.

But here’s the interesting point Silver is getting at: It’s likely that those 30 races will fall definitively one way or the other, instead of splitting 50/50.

Undecided voters may overwhelmingly break one way at the very end (possibly because of some external event that neither side can control)—or the turnout model used by pollsters this cycle may have a consistent flaw that favors one side over the other.

It is amazing (and sobering) that even if one party wins all 30 races, those victories could be decided by a few thousand voters.