Why late shifts in the polls probably won’t help Democrats in Senate races

The Washington Post reports:

All of the major Senate forecasting models, including ours at Election Lab, now rely heavily on averages of public polls. This raises the question of whether those averages will be correct on Election Day, and whether any misses could affect which party manages to retain control of the Senate. In particular, there is the question of whether polling misses might mean that the Democrats end up with a slim Senate majority after all.

There are reasons to be skeptical that this will happen. It’s not just that we can’t easily predict whether the polls will over- or underestimate one party’s vote share, as discussed by Nate Silver and by Mark Blumenthal & Co. And it’s not just, as Josh Katz and Sean Trende have found, that Senate polls already tend to be pretty accurate at this point in time — especially when candidates have a 3- to 4-point lead, as do Republican candidates in Alaska, Arkansas, Georgia, Kentucky and Louisiana.

The other key point is this: Late movement in Senate polls tends to be in the direction of the underlying fundamentals.

Just a reminder.