It's not about nebulous concepts like "mandates." And I doubt we'll ever see another Reagan/Mondale map again.Is 55 to 41 a blowout? We always see headlines like "mandate" and "overwhelming" at that kind of margin and while it's uncommon, I think of a blowout more like 80/20. Not sure that's ever happened in a US election.
A 14-point generic ballot means Republicans will lose safe seats. The 2018 generic ballot was D+8.4. Dems won the House 235-199. This is nearly twice that number, and Trump's policies haven't even begun to hurt yet.
In the Senate, North Carolina and Maine were already on the table. You can add Ohio, Florida, Texas, Iowa, and Montana. If you get a strong candidate in Nebraska, Kansas, Missouri, etc., those states could be up for grabs, too.