Ticket-splitting isn’t that hard, after all. It has declined in recent years because of the polarization of the electorate and the convergence on issues of each party’s presidential and congressional candidates. That started in the 1990s when Bill Clinton’s policies cost Democrats congressional seats in anti-gun-control territory but increased his own appeal in upscale Northern suburbs.

It continued in the 2000s as congressional Republicans ran on George W. Bush’s record, making small gains in 2002 and 2004 and suffering big losses in 2006 and 2008. It has continued in the Obama years, as the number of moderate congressional blue dog Democrats plunged toward zero.

But Donald Trump is plainly something different and distinct from almost all congressional Republicans, both leadership supporters and tea party rebels. Voters clearly recognize this difference, with non-college whites more favorable to him than Mitt Romney and college graduates less so. Most Senate Republican candidates in close races are incumbents who established their own distinct records long before Trump rode down the Trump Tower escalator and announced his candidacy.