With just about three weeks to go until this campaign is put out of its misery, we find Donald Trump impossibly behind and the Hillary Clinton campaign and her allies pushing to expand the map. The question isn’t whether Clinton wins, it’s now a question of by how much. The bigger the margin, the better the odds of Democrats down ballot success. While most Republican senators and many incumbent representatives are currently polling ahead of Trump, it gets much harder for them to hold on if Trump is losing by more than six or seven points. But, there’s another reason that Clinton should want to win big. Theoretically, a blowout win makes it easier for her to dismiss the “rigging” arguments, humble rebellious Republicans in Congress and give her more of a mandate to govern. Given some of the structural challenges Clinton faces, however, I am skeptical that these theories can actually come to pass. First, let’s look at the electoral math. As my colleague Charlie Cook wrote the other day “It’s getting increasingly difficult to characterize the presidential race

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