worries that Donald Trump will make it easier for the eventual Republican nominee to win the presidency by making him seem moderate by comparison. Marcotte admits that her scenario assumes that Trump crashes and burns at some point, and one of the other candidates (probably Marco Rubio or Ted Cruz) wins the nomination.
Marcotte is careful to admit the possibility that Trump might not crash and burn at all, and might win the Republican nomination himself. However, I think that even if Trump doesn't win the nomination, his candidacy will make a GOP victory less likely rather than more. Over the course of Trump's campaign, I've noticed that his success in appealing to the worst instincts of the GOP base has had the effect of goading the rest of the Republican candidates into emulating him. It's reached the point where alleged moderate Ohio Governor John Kasich is now promising to create a new federal agency to promote "Judeo-Christian Western values" in the Middle East.
What this means is that even if Trump does drop out of the race at some point, the rest of the GOP field will already be so over-the-top crazy trying to keep up with him that they won't be able to stop. Trump has already established that that's the way to win, and which of his competitors will dare try to change that winning formula? By the time the Republicans hold their convention in Cleveland in July, the nominee (whether it's Trump or someone else) will be committed to a full-bore racist agenda. Everyone in the country who isn't a straight-up racist will be voting Democratic, and Barack Obama proved that there are enough Americans out there who aren't straight-up racist to ensure a Democratic victory.