This article was written and published before the release of the audio of Donald Trump's offensive comments to Access Hollywood's Billy Bush.

When the majority is at stake, the battle for the control of the U.S. Senate always becomes a math equation. What combination of seats will get one party or the other to the magic number? For Democrats this cycle, that magic number is four seats if Hilary Clinton wins the White House, or five if she isn’t successful. As recently as late spring, it didn’t seem like hitting the four- or five-seat mark would be all that difficult, and the question was more about how large of a majority Democrats could build. It now seems as if they will have to work for those four or five seats. At the outset, it is worth stating that we continue to expect Democrats to score a net gain of between four and six seats. At the same time, there is now a narrow and steep path for Republicans to maintain their majority by their fingertips. This makes the math

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