Gallup’s historical model suggests that a party needs at least a two-point advantage in the national House vote to win a majority of the 435 seats. The Republicans’ current likely voter margin suggests that this scenario is highly probable, making the question of interest this election not whether the GOP will win the majority, but by how much. Taking Gallup’s final survey’s margin of error into account, the historical model predicts that the Republicans could gain anywhere from 60 seats on up, with gains well beyond that possible.
It should be noted, however, that this year’s 15-point gap in favor of the Republican candidates among likely voters is unprecedented in Gallup polling and could result in the largest Republican margin in House voting in several generations. This means that seat projections have moved into uncharted territory, in which past relationships between the national two-party vote and the number of seats won may not be maintained.