A 10-point shift from Biden’s 51 percent showing in 2020, universally applied, would imply that a Republican candidate would win the popular vote by about 5.5 points. A 12-point shift would give the GOP a 7.5-point advantage. That latter advantage approximates George H.W. Bush’s margin over Democrat Michael Dukakis in 1988 and could give the Republican nominee as many as 358 electoral votes. That alone would reduce the Democrats to a regional rump party based largely on the Pacific Coast and the upper Northeast.

It would be even worse in the Senate, where Republican gains could propel them to record highs. Democrats will defend 12 seats in 2024 where Biden’s 2020 margin was 12 points or less, including Maine’s seat held by Sen. Angus King (I), who caucuses with the party. A repeat of Tuesday’s margin shift here would likely cause more of them to lose, possibly giving Republicans more than 60 seats. To put that in perspective, the GOP has never had more than 60 seats since the direct election of senators started nationwide in 1913.

Democrats held 257 House seats and a filibuster-proof 60 seats (achieved after moderate Sen. Arlen Specter switched parties) in the Senate in 2008 following two consecutive elections that featured 10-to-13-point margin shifts from 2004. That let them pass Obamacare and decisively move the country to the left. After Tuesday’s results, a Republican majority of that magnitude is no longer a pipe dream.