Updated Oct. 22, 2018, at 1:24 PM

If the Senate is split 50-50, Republicans maintain majority control because Vice President Mike Pence has the tiebreaking vote. This analysis treats independent Sens. Bernie Sanders and Angus King as Democrats because they caucus with that party.

# Our forecast for every Senate seat

The chance of winning for each candidate in the 35 Senate elections taking place in 2018, as well as the controlling party for the 65 seats not on the ballot this cycle.

The balance of power

The state of every state

Not up for election
Up for election

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# How much each race matters

Two measures help capture how important a state and its voters will be in determining which party controls the next Senate: “Tipping-point chance” is the probability that a race will decide whether the Democrats or Republicans are in the majority. “Voter power index” is the relative likelihood that an individual voter in a state will determine the majority party.

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# How the Senate has swung historically

Our forecasted seat breakdown in the Senate for 2018 and the change in the breakdown for every Senate election since 1924.

How this forecast works

Nate Silver explains the methodology behind our 2018 midterm forecasts. Read more …