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

On average, the polls have not yet fully incorporated even these basic fundamentals by this point. After today, 18 days before the election, there tends to be further movement toward those fundamentals. The sharp movement in the last few days of the campaign should be taken with a grain of salt, since the volume of polling drops over the weekend before Election Day, but the overall pattern is clear.

As we noted back in January, a slightly more elaborate fundamentals-based forecast based on elections since 1980 favors the Republicans. And this is what poses a challenge for the Democrats: Right now they need the polls to move in their favor, but in key states this would entail movement opposite to what the fundamentals would predict and therefore opposite to the trend above.