The one and only reason.
Trump may be a fraud. Even if he is not, he is not "one of us." Any WN who wastes time, energy, and money actively supporting Trump's candidacy is an idiot.
But there is a reason, one reason, the only reason, to consider making the trip to the polls to vote for Der Touchback if he's on a ballot (primaries, if you are a registered idiot [i.e., Republican], or in the general election if Trump is on the ballot as a Republican or an Independent).
It is not because "he'll do something about immigration." It's not because you should have some Roissy-like heavy breathing sexualized fetish for "Der Trumpening." It's not because an obnoxious, mercurial buffoon would make a good President.
No, it is this: whatever Trump really is, the public perception of him is that he is a pro-White, anti-immigration "fascist" right-wing populist. Assuming that perception holds - and that "alpha male Trump" doesn't start groveling and moving to the Left out of desperation - then Trumps's success has certain advantages.
Assuming the public perception of Trump as a combination of Pat Buchanan and Huey Long, with a dash of David Duke thrown in, holds, then significant support for Trump will greatly increase racial and cultural balkanization in America, it will "throw a monkey wrench" into the smooth running of the multicultural regime, it will undermine public confidence that "we all can get along," it will enrage Coloreds and their White enablers, it will increase the animus between the GOP Establishment and the White grass-roots: in a word, it will cause chaos, Chaos, CHAOS, CHAOS, CHAOS.
If people really believe Trump is what he really is not, and if they believe a significant portion of Whites support that straw man image of Trump, then the System is weakened and undermined.
And for that, if for nothing else, a vote for Trump is useful (again assuming he doesn't start backtracking publicly, which would invalidate this whole thesis).