Gallup's Final GCB at +15%

Gallup's final generic congressional ballot survey shows Republicans at 55% and Democrats at 40%.  This predicts a national two-party congressional vote of Rep 58%, Dem 42%.  According to one set of 1000 Monte Carlo simulations taking into account the heavy Democrat incumbent advantage, this negative 16% D result implies that the next House could split 243 R to 192 D, a net Democrat loss of 64 seats, and a larger Republican majority and a smaller Democrat minority than any since 1946.

About this, Gallup says

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.

My face hurts from grinning so much!

Control of the Senate hangs in the balance and depends on turnout in California, Washington, Illinois, and West Virginia.  Except for West Virginia, the states on that list are usually heavily Democrat, and that's the reason that Senate control is less likely to pass to Republicans than the House.  For more on that, see Sean Trende's analysis here.