If Trump wins, he will remake the party entirely in his image. But because he cannot govern himself, he cannot govern the country. By the end of his presidency (whether it comes via impeachment or voter rejection in 2020), the GOP will be a smoking ruin.
.. If Trump loses, he won’t go away. It will be all-Dolchstosslegende, all the time (Drumpfstosslegende?) He will be a constant presence on the public scene, hectoring the Republican Party, denouncing its leaders for betraying him, and keeping his base riled up. Because of his big mouth and gift for self-promotion, he stands to make himself, not Congressional Republicans, the voice of opposition to President Hillary Clinton.
.. Did Trump destroy the GOP? Of course he did. But you could also argue that the Bush family did, first by the presidency of George W., and then by the fact that Jeb Bush, early in the primaries, blew a fortune in donor cash to destroy Marco Rubio. Rubio not only may have been the only Republican who had a chance at beating Trump, but it’s also true that money spent to annihilate his candidacy was money not spent on stopping Trump.
The outlines of the two-party system of the 2020s and 2030s are dimly visible. The Republicans will be a party of mostly working-class whites, based in the South and West and suburbs and exurbs everywhere. They will favor universal, contributory social insurance systems that benefit them and their families and reward work effort—programs like Social Security and Medicare. But they will tend to oppose means-tested programs for the poor whose benefits they and their families cannot enjoy.
They will oppose increases in both legal and illegal immigration, in some cases because of ethnic prejudice; in other cases, for fear of economic competition. The instinctive economic nationalism of tomorrow’s Republicans could be invoked to justify strategic trade as well as crude protectionism. They are likely to share Trump’s view of unproductive finance: “The hedge-fund guys didn’t build this country. These are guys that shift paper around and they get lucky.”
The Democrats of the next generation will be even more of an alliance of upscale, progressive whites with blacks and Latinos, based in large and diverse cities. They will think of the U.S. as a version of their multicultural coalition of distinct racial and ethnic identity groups writ large. Many younger progressives will take it for granted that moral people are citizens of the world, equating nationalism and patriotism with racism and fascism.
The withering-away of industrial unions, thanks to automation as well as offshoring, will liberate the Democrats to embrace free trade along with mass immigration wholeheartedly. The emerging progressive ideology of post-national cosmopolitanism will fit nicely with urban economies which depend on finance, tech and other industries of global scope, and which benefit from a constant stream of immigrants, both skilled and unskilled.