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Tuesday, June 19, 2018

A Good Illustration of a Polling Truth

Heidi Heitkamp is a Democrat senator from North Dakota.  She is also a Democrat running for re-election in a state in which Donald Trump destroyed Hillary Clinton in 2016.  There's a poll out today showing that Heitkamp is losing to her Republican opponent Kevin Cramer by 48% to 44%.  It's a very bad omen for Heitkamp even though we still have almost five months left until election day.

The poll, however, is also a very good illustration of a basic truth of polling in races involving incumbents.  If the polls show an incumbent with less than 45% of the vote, that candidate is in trouble.  Remember, the voters already know the incumbent well and have formed an impression of that person.  The voters who like the incumbent already know that.  Similarly, the voters who do not like the incumbent have pretty much fixed that opinion as well.  Four months ago, there was another poll in the Heitkamp/Cramer race that showed Heitkamp ahead by 43 to 40%.  While Heitkamp was ahead, she was under 45%.  Since then, her numbers are essentially unchanged while Cramer has gone up by 8% with voters moving from undecided to Cramer. 

Obviously, things could change by election day.  Nevertheless, if you use this rule of thumb about the 45% for the incumbent, there is also a clear indication of trouble for Democrat Claire McCaskill in Missouri (who leads her GOP opponent by 45 to 43.5%).  The same is true in Indiana where the GOP candidate leads in the only polling.  In Nevada, Republican incumbent Dean Heller leads his opponent by just 1% at 40 to 39%, an indication of trouble for the incumbent there too.

 

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