Partisan Lean
At Race to the WH, Partisan Lean refers to two things.
First Meaning
First, it’s a way to describe how likely each party is to win the state. You’ll see it used this way on the main page for the Senate and Presidential Forecast. There are nine types - which are broken down right below.
Detailed Breakdown - Safe, Likely, Lean, Tilt and Tossup States
Safe Democrat/Republican - 95%+ Chance of Winning: One party is the clear and dominant frontrunner, and the election likely won’t be close. However, upsets are certainly not impossible. Remember to always think in probabilities. If there are 20 races with a 5% shot of an upset, don’t write them all off. The leading party will lose one of those on average.
Likely Democrat/Republican - 85-95% Chance of Winning The frontrunner has a decisive advantage, but upsets will happen from time to time. The most high profile upset of this kind in our forecast would have been Wisconsin in 2016 - so don’t make the mistake of taking these races for granted.
Leans Democrat/Republican - 75-85% Chance of Winning - These races may have shifted towards one party, but they are very much in play. frontrunner have a real edge, but no one should be surprised to see the underdog win. They have a 75-85% chance of winning
Tilt Democrat/Republican - 65-75% Chance of Winning - While one party has gained an upperhand, these races tend to be quite fluid, and far from secure victories.
Tossup - These are the ultra-competitive elections. Both parties have somewhere between a 35-65% chance of winning.
The Second Meaning
The second meaning of partisan leans refers to the projections for individual Senate Races, and for the Presidential Battleground States Forecast. Here, it refers to how much voters in the state have preferred Democrats or Republicans compared to the nation at large over the last few elections. Let me give you an example. In 2018, Americans nationally prefered Democrats to Republicans by 8%. If Iowa voted for Democrats by 5% more than Republicans, that would still be less the nation at large, so it would have a partisan lean of 3% towards Republicans. In other words, we might expect it to vote for Republicans by 3% if the race national vote was tied.
The lean is calculated a little bit differently both the Presidential and Senate Forecast. For the Presidential forecast, the lean is made up of three years - 15% from 2018, 68% comes from 2016, and 17% from 2012. For the Senate Forecast, 37% comes from 2018, 55.6% comes from 2016, and 7.4% comes from 2014. For both formulas, we use the Presidential race to calculate the lean from years where there was a presidential election, and we use the House of Representatives for midterm years. We take care to make sure the average isn’t skewed by house races where a candidate runs unopposed.
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