While I don’t think future declines will accelerate exactly quite as much as the August to September period, I do think that Democrat fortunes will continue to fall at a more modest rate for the remaining two months of the campaign season. Thus, assuming declines roughly equal to the declines in those first months and distributing them evenly to all of the races, and Democrats are looking at 52 seats that are just toss-ups or worse on election day. From seat 53 to seat 77, pretty much anything can happen, as all are between the toss-up and lean Democrat categories. Seat 78, currently Dan Maffei’s NY-25, looks to be the high end of GOP gains. However, assuming the GOP wins a third of those intervening seats, the math is pretty straightforward: about 60 new GOP seats.
This all assumes some pretty fierce wave action, which I think is reasonable to believe will happen. Moreover, the 60 most vulnerable seats listed are simply the most likely to me to flip; given the countless factors at the macro and micro levels, the actual list of 60 flipped seats will be different. Regardless of the particular Ws and Ls, the seismic political impact would be the same.