Does Brexit Mean We’re Doomed?

I suspect we’re going to see a lot of this kind of analysis:

Britain’s stunning vote to leave the European Union suggests that we’ve been seriously underestimating Donald Trump’s ability to win the presidential election.

When you consider all his controversies and self-inflicted wounds over the past month, combined with how much he’s getting outspent on the airwaves in the battleground states, it is actually quite surprising that Trump and Hillary Clinton are so close in the polls. He’s holding his own, especially in the Rust Belt.

Does this make sense? Not really:

• I mean, on one level it’s scary that Trump is within 6 points. But, still 6 points, in presidential election terms, is getting your ass kicked. And there’s no reason to think he has much upside potential.
• It might be possible for a formidable campaign organization to overperform the polls. But Trump has the opposite of that. Clinton’s dominance of the airwaves and superior organization is going to make it harder for Trump to overcome a substantial deficit and harder to get his supporters out.
• The argument against these facts seems to be something like “nobody expected Brexit to win, nobody expected Trump to win, but Brexit won, and Trump has already won once, so Trump can win twice.” But this doesn’t really make any sense. Unlike with Brexit, Trump took a commanding lead in the polls early on in the primaries; skeptics (like me) were ignoring the polls. I don’t think there’s any reason to believe there’s a large reservoir of untapped support for Trump that polls aren’t picking up.
• One major comparative advantage for Brexit is that none of the prominent assholes on its side were actually on the ballot. People who would never dream of voting for Nigel Farage or Boris Johnson in a national election could vote Brexit. Implicitly voting against Cameron didn’t require voting for someone you hate as much or more. If the question on the ballot in November was “do you want Hillary Clinton to be president?” I would be pretty worried. But it’s not. If Trump is going to win, he’s going to need a plurality of voters to affirmatively vote for him, although he’s a very well-known and widely despised figure heading a nationally unpopular party while barely running a presidential campaign at all.
• The United States is a much bigger and more diverse country, which really makes a big difference in terms, which is rather important for how a campaign based around mobilizing white resentment will play out. How is Trump going to win Florida, barely a white majority state? What’s his path to the Electoral College without it? (Hint: even if he can win Ohio and Pennsylvania, that’s not enough.)
• Brexit is helpful to Trump for one reason only: if it harms the American economy, it hurts the incumbent party. Will the effects on the American economy be enough to make a big difference? I doubt it, but that’s the only reason to worry about Brexit in terms of the American presidential election.