Hey, these Republicans aren't guaranteed to win

Democrats Tend To Perform Better Than Polls Predict

Even in the week before the election, polls are not perfect. For example, in two out of ten close Senate races in 2010 and 2012. In those two cases, both in 2010, the eventual winner was the Democrat (Harry Reid in Nevada and Michael Bennet in Colorado). This reflects a broader pattern: When errors occur, the outcome tends to be more favorable to the Democrat…

Overall, these numbers set a range for how wrong we would expect a poll-based view to be. Overall, pollsters as a group underestimate Democratic performance by an average of 1.2 percent. This bias is asymmetric: When Republicans outperformed, they did so by 1.2 percentage points or less. But in four out of eight cases, Democrats surpassed polls by 2.4 to 3.7 percentage points. This bias was even larger in Colorado, where Democrats outperformed polls by at least four percentage points in the 2010 and 2012 elections.