Senate Forecast Update, August 9th

by: Chris Bowers

Mon Aug 09, 2010 at 20:26

Senate Picture, August 9th, with Rasmussen
Most likely outcome: Democrats 52 seats, Republicans 47 seats, Charlie Crist 1 seat

Of the 100 Senate seats, 86 are either not up for re-election, or have a polling average where one party has a 100% chance of victory (if the election were held today).  Among those 86 seats, there are 48 Democrats, and 38 Republicans.  Here is a chart featuring the other 14 campaigns:

Senate picture, competitive campaigns chart, August 9th, with Rasmussen

The 48 currently safe Democrats, plus the 4.20 wins projected in these 14 campaigns, comes out to 52.20 Democrats, or 52 seats.  Charlie Crist is also projected to win one seat.

Senate Picture, August 9th, without Rasmussen
Most likely outcome: Democrats 54 seats, Republicans 45 seats, Charlie Crist 1 seat

Senate picture, competitive campaigns chart, August 9th, without Rasmussen

The 48 currently safe Democrats, plus the 6.00 wins projected in these 14 campaigns, comes out to 54.00 Democrats. Charlie Crist is also projected to win one seat.


  • Methodology here
  • All polls taken from
  • * = Has primary challenger, but heavy favorite
  • The "current Dem winning %" column projects the chance of Democratic victory if the election were held today.  It is not meant to predict the chance of the Democratic candidate winning in November.
  • Every Senate seat not listed here currently has either a 0% or a 100% chance of a Democratic victory.
  • Knedrick Meek is projected as the winner of the Florida primary because he leads in 3 of 4 polls, even though Jeff Greene narrowly leads the average.
Very little overall change in the numbers from last week, but that really isn't surprising for August.  Outside of the states which still have primaries, the major ad buys will not begin until after Labor Day.  Still, it won't be long before I am posting an update to the forecast every evening.

Also, I ran the 25-day simple mean methodology against another forecasting giant, Real Clear Politics.  Across the 48 Presidential, Senatorial, and Gubernatorial general election campaigns with the closest final polling averages since 2008 where Real Clear Politics made a final projection, the 25-day simple mean was much more accurate:

Real Clear Politics
Mean Error: 2.91
Median Error: 2.14

25-day simple mean
Mean error: 2.39
Median error: 1.65

That's a big gap in accuracy between the two methodologies.

The error being measured is final projected margin to final actual margin. Dave Leip's Atlas of Elections is used as the source for the final margin.  You can see all of the work backing up these claims here.

Chris Bowers :: Senate Forecast Update, August 9th

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Turnout/Could Crist Decide? (0.00 / 0)
I understand that polls are just a snapdhot but I sure think Robin Carnihan has better than a 7% shot and that Boxer has far more than a 3% chance of blowing it.  I think 2010 is going to blow away some of the assumptions regarding turnout and that could sway several races. I'd love to see a discussion if the assumptions the pollsters use regarding turnout.  They sure often manage to get it wroung in low turnout contests such as the Iowa Caucuses.  Early voting is another wild card and a relitively recent phenomonon.  I wish our side spent more money on turnout and less on TV.

It looks to me that if Dems have a really, really bad October there is a small chance that turncoats could decide control of the Senate.  A coalition or just one of, say, Sen. Crist, Holy Joe & Ben Nelson could really upset the northern side of the Capitol.

Win Percentage (0.00 / 0)
I forgot the methodology for it, but the win percentage was explained in detail in the last Senate forecast. Chris isn't making November predictions- that's the percentage chance that they would win if the election were held today.

[ Parent ]
Anyone who says they can predict something as (0.00 / 0)
nonlinear as the Iowa caucus, where second and third choices are as important as they are, and outcomes are so precinct dependent, is overstating their case.  

[ Parent ]
Turnout (0.00 / 0)
Cycle after cycle millions are spent polling Iowa and the turnout almost always exceeds expectations -- 2008 and 2004 are the latest examples -- throwing the models off.  

I think that the story of 2010 is going to be turnout and right now the conservatives are motivated and progressives are not.  It sure was the story of 2009 when Democrats got buried in Virginia and upset in New Jersey.  I wish I heard more about how progressives are going to motivate base voters and, frankly, less about how we can run to the center.   It's going to take a lot more then scarey talk about how bad the Sharon Angle's and Rand Paul's of the world will be.

[ Parent ]
turnout is one thing (0.00 / 0)
but a deeply nonlinear relationship between voter preferences and delegate counts is a close second.  There was absolutely no way to predict if Obama or Edwards or Clinton were going to win in Iowa--it was far dependent on too many things, and far too sensitive to small numbers of voters changing their minds, or changing their second choice, or a random snowstorm.  Any model for predicting caucus outcomes is a rough first-order estimate.  
Polls are rarely that far off with primaries and elections for a reason.  

[ Parent ]
I can't understand how Toomey is still doing so well (0.00 / 0)
even in the sans-Rasmussen polling.

Yeah, I"m amazed that Rand Paul hasn't been trending (0.00 / 0)
downward as well.  

[ Parent ]
Maybe Kentucky really wants Rand Paul (0.00 / 0)
why does this come as a shock to people?  

[ Parent ]
Because he's a nonstop gaffe machine (0.00 / 0)
who has a haistory of sexual assault.

[ Parent ]
Again, why does this come to a shock to people? lol (0.00 / 0)
he's a Republican, in stupid red states, that shit only matters if you're a Democrat.  

[ Parent ]

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