Will there be a late break? As we learned in 2016, and in a less dramatic fashion in 2014, a late break in the races can alter the landscape substantially. This year, there are a lot of undecided voters remaining. Look at the most recent House polling from the New York Times/Siena: In some races, the leading candidates are at 43 percent (IA-03), 45 percent (UT-04, PA-10, NJ-03), and 44 percent (NY-11). Moreover, the trailing candidate is typically only behind by a point or two.

This adds up to a situation where a slight break in the undecideds toward one party or the other could be the difference between a healthy Democratic majority and a slim Republican one. My standard answer to how these races will break is to assume that, on average, they will converge on the president’s job approval, but there still is enough “wiggle room” in that political tendency to move things either way.

Given the closeness of many races, and the president’s improving overall job approval, it is also unclear how to evaluate this in the current cycle. In New York’s 22nd Congressional District, Siena College places the president’s job approval at 53 percent, so Republican Rep. Claudia Tenney is possibly in better shape than her polling numbers suggest. But what about the 19th District, where Rep. John Faso is up by a point, but the president’s job approval is at a 46/49 split? That suggests a very close race, and there are likely a lot of districts with splits like this one.