I don't think the 1996 example holds water for another reason. Bill Clinton basically coasted to reelection. I'm pretty sure I remember reading in his autobiography (which I bought and read 12 years when I was 17) that he basically admitted he could have won by a few more points and won a few more states. If Republicans try to fall back on Congress, I don't think Democrats are going to let them do that without a fight like they did in 1996. I mean, looking at the results from 1996, there's no reason why Democrats shouldn't have won back the House. They only had a +2 net gain from 1994. Democrats just didn't run a good campaign. Bill Clinton should have won by 15 points and at least 40 states and Democrats should have easily taken the House back. I could also excuse not winning the Senate back, but Republicans actually gaining two seats is absolutely not (the worst offense being losing a Senate seat in President Clinton's home state).
I don't think Republicans can really do much to save the Senate. If anything, the map is actively moving away from them. Charlie Cook currently has nine tossups (8 Republicans, 1 Democrat). On average, the tossups tend to go about 80% to one party overall. Since 1998, one party has always won between 67-89% of the tossup races. They're not going to split down the middle. It just doesn't work like that (
see here).
As for the House this year, it's really too early to say. I agree with most people that say that it would take a wave (i.e. anywhere from a solid Clinton win to a landslide) for Democrats to win back the House. That cake isn't even done mixing, let alone ready to bake. I don't think we'll know the true House landscape until after the first debate. Waves really tend to materialize in October. I think there will be races not on the radar that will be if we're at this point in late September (which basically has to happen if a Democratic takeover is to actually happen). Split-ticket is sure to increase this year, but if Trump is losing suburban Republican-held seats by 15 or even 20-points or more, very few will survive. No gerrymander will protect against a 40-point or even a 2-1 Hillary win in the Philly suburbs (which is the current polling). I think it's general political conventional wisdom with gerrymanders that the bigger they are, the harder they can fall. I think it will take a sizable win for the House to fall, but it is a significant possibility that cannot be ignored.
