I like to post this polling “spread sheet” heading into important primaries to test the accuracy of polling.
I can update this as new polls come in on North Carolina and Indiana leading up to Tuesday’s voting.
Real Clear Politics has what it calls the “RCP” average for predicting election results. It takes the latest polls and averages them together to get a predicted outcome.
This system is used frequently on Cable News and is often called the “poll of polls.”
Below is a look at the RCP “poll of polls” margin of victory prediction and the actual results.
The results are from Primary states. Caucus states are not included so that we have (as much as possible) an “apples to apples” comparison to the polling data for North Carolina and Indiana.
There are no available “RCP Poll of Poll averages” for Primaries held in several states including Delaware, Mississippi, Vermont and Oklahoma. This was probably due to the lack of available polling.
This left Real Clear Politics’ “polls of polls” available for 20 primary contests.
I separated the RCP results into the following categories.
RCP was extremely accurate (within 3 points) 45% of the time.
9 contests
Pennsylvania RCP… Clinton +6.1 Results … Clinton + 9.2
Technically the polling average was off by 3.1 but it wasn’t wildly inaccurate so the results were included here.
New Jersey RCP… Clinton +9.8 Results … Clinton +7.7
New York RCP… Clinton +17.2 Results… Clinton +17.5
Illinois RCP… Obama +33 Results… Obama +31.5
Arizona RCP… Clinton+ 6 Results… Clinton +8.8
Tennessee RCP… Clinton +13.3 Results… Clinton +13
Ohio RCP… Clinton +7.1 Results… Clinton + 10.1
Maryland RCP… Obama 22.3 Results… Obama 23.5
Texas RCP… Clinton + 1.7 Results… Clinton +3.5
RCP predicted the correct winner but the margin of victory (outside of 3 points) was wrong 30% of the time.
6 contests
South Carolina RCP… Obama + 11.6 Results… Obama + 28.9
Virginia RCP… Obama +17.7 Results… Obama +28.2
Wisconsin RCP… Obama + 4.3 Results… Obama + 17.4
Rhode Island RCP… Clinton + 9.7 Results… Clinton + 18
Massachusetts RCP… Clinton + 7.0 Results… Clinton + 15.4
Georgia RCP… Obama + 18 Results… Obama + 35.3
RCP predicted a margin of victory for the wrong winner 25% of the time
5 contests
New Hampshire RCP… Obama +8.3 Results… Clinton +2.6
Connecticut RCP… Clinton + 4.0 Results… Obama + 3.1
California RCP… Obama + 1.2 Results… Clinton + 9.6
Alabama RCP… Clinton + 1.2 Results… Obama + 14.1
Missouri RCP… Clinton +5.7 Results… Obama + 1.2
Quick take home points.
RCP’s average of the best pollsters in the country yields the right winner 75% of the time or 3 out of every 4 contests.
The average of the best pollsters in the country yields the wrong winner 25% of the time or 1 out of every 4 contests.
The 5 contests(25% of the time)where the RCP predicted the wrong winner, 3 of the 5 contests (60%) were won by Obama.
In the 6 contests were the RCP has the winning candidates margin off by 3 points or more,(30% of the time) again it was Obama’s support that was underestimated in 4 of the 6 (67%) results.
Only in Massachusetts and Rhode Island has Clinton exceed her RCP predicted margin of victory by 3 or more points. (Pennsylvania 3.1)
The RCP polling average had the correct winner and the correct margin of victory (within about 3 points) in 9 contests or 45% of the time. Hillary Clinton was the winner in 7 of 9 or 78% of the time.
Here are the current RCP averages for Indiana and North Carolina.
North Carolina Obama… +8.2 Results… TBA
Indiana Clinton… 6.2 Results… TBA
You can find all of this information at Realclearpolitics.com
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