The Eric Cantor Upset: What Happened? | FiveThirtyEight

In a shocker, House Majority Leader Eric Cantor has lost the Republican primary in Virginia’s 7th Congressional District to a relatively unknown college professor, David Brat. Brat spent little money in the race; Cantor spent over a million dollars. The political media will spend days trying to figure out what happened, but here are a few quick thoughts.

First, this race had a heavy insider vs. outsider dynamic, and the tea party is definitely not dead. As my colleague Nate Silver pointed out previously, it was probably too early to call for the tea party’s demise. Cantor’s loss puts an exclamation point on that.

One last thought: This race is another example of why you shouldn’t trust the internal polls put out by candidates. Just a few weeks ago, Cantor released a survey showing himself up 34 percentage points. A public poll had the race much closer, with a 13 point lead for Cantor. I’ve written about the bias of internal surveys released to the public. We should assume that internal polls are biased and misleading — unless we have a good reason to think otherwise.

In this case, we knew what we were getting with Cantor’s polling firm, McLaughlin & Associates. As demonstrated by Daily Kos Elections, McLaughlin has gotten many races wrong in the past two years. In Virginia, it had Mitt Romney and U.S. Senate hopeful George Allen winning their 2012 races easily. Both Republicans lost by a significant margin.

Despite Cantor’s McLaughlin poll, it was clear in the final weeks that he thought he was in trouble. He spent a lot of money on negative advertising against a little-known opponent. Compared with the polling he put out, he knew something we didn’t. Sometimes it’s better to follow the money and watch what the campaigns are doing than to listen to what their pollsters say.

via The Eric Cantor Upset: What Happened? | FiveThirtyEight.