The Republican Party’s post-mortem after Mitt Romney lost his presidential bid to Barack Obama in 2012 was brutally straightforward: Expand the tent or risk extinction. “We need to campaign among Hispanic, black, Asian and gay Americans and demonstrate we care about them, too,” party leaders wrote.

Regardless of the results on Tuesday, that playbook is gone, burned and buried, and it is not going to be easy to retrieve it from the dump. The Republican Party is now the party of President Trump.

The dark politics of anger, division and fear were on display in campaigns across the country this year, as Republican candidates for Congress and governor — and fringe groups who support them — embraced the racially inflammatory brand of politics that Mr. Trump unleashed in 2016. With the presidential campaign of 2020 effectively underway on Wednesday, there is little reason to think Mr. Trump will back away from a tactic that clearly rallies his base.

[See the results for governors’ races, the House of Representatives and the Senate.]

And as he showed his party in the closing days of the midterms, there may be no way for Republicans to escape his shadow.