Why some polls may be underestimating Democrats

In five of the seven races polled, the Democratic candidate either did better or no worse when Monmouth switched from registered voters to likely voters. And in the two races where the Republican candidate does better with the switch to likely voters, the change was 2 points or less.

The average shift has been 2 points in favor of the Democratic candidate.

A 2-point shift may not seem like a lot but it could be huge if it holds across the board. Democrats right now hold roughly a 7-percentage point edge on the generic congressional ballot. That’s right in the area where they need it to be to have a net gain of 23 seats to take control.