How the pollsters fared

CNN -The generic ballot isn't a perfect estimate of the House popular vote because often pollsters don't mention the specific candidates running in each district and some districts don't feature candidates from both parties running. Still, these factors tend to cancel each other out nationally and are only worth a point or 2 at the very most. They don't excuse Rasmussen's midterm performance. Rasmussen's final poll was the least accurate of any of the 32 polls. They had the Republicans ahead nationally by one point. Democrats are currently winning the national House vote by 8.6 points.

Looking at all pollsters, the average poll hit the mark nearly perfectly. The average gold standard poll (i.e. ones that use live interviews, calls cell phones and is transparent about its practices) over the final three weeks of the campaign had Democrats ahead by 9.4 points on the generic congressional ballot. That's an error of less than a point. The average pollster overall, according to the FiveThirtyEight aggregate, had Democrats up by 8.7 points. Once all the votes are counted, that could have hit the nail on the head.