As the final, frenzied push towards the first presidential voting begins, Donald Trump has unveiled a riveting new television ad that perfectly sums up Trumpism in all its xenophobic glory — and also perfectly captures the problem Trumpism has created for the Republican Party.The ad, which is set to run extensively in Iowa and New Hampshire, has it all. It reiterates his call for a temporary ban on Muslims entering the United States, and links this directly to the need to combat “radical Islamic terrorism.” It also again vows to “stop illegal immigration by building a wall on our southern border that Mexico will pay for.” All of this leads up to the grand conclusion, in which Trump himself vows to “make America great again.”Note this footage from the new Trump ad showing dark hordes breaching the border. . . . . this depiction of “illegal immigrants as invaders” offers a striking parallel to today’s Trumpian rhetoric. That parallel should make it hard to avoid reckoning with the possibility that Trump’s appeal to GOP voters just might be partly rooted in the raw appeal of his xenophobia and demagoguery about immigrants, and not just in anxieties that are legitimately traceable to the impact of immigration policy on GOP voters’ economic prospects, as some right-leaning commentators have suggested.[A]s one California Democrat puts it to Dionne: “The one thing no one can stop is that every month, the rest of America looks more like California.”Other Republicans, such as pollster Whit Ayres, broadly agree with this analysis and its ominous portents for the GOP’s hopes in future national elections. Now, it remains unlikely that Trump will actually win the nomination. But even if he doesn’t, the question then becomes: Whither the forces Trump has unleashed inside the GOP? Trump’s candidacy — and to a somewhat lesser extent, that of Ted Cruz — is framed around the idea that the way to win the White House is by unleashing the power of white backlash.