Are we demeaning a presidential election by saying it is reducible to sound bites? I once thought so. Until it became clear that Donald Trump, like Bernie Sanders, was somehow detecting the complex tectonic shifts inside American politics.

Some of these shifts are disturbing—blue-collar alienation, eroding civil order in some cities—but unlike his always-hedged opponent, Donald Trump slams into them.

This sort of populism is exciting, but often limited.

Bernie went down because he was too one-note. Inequality wasn’t enough. Donald Trump’s one-note is trade, but his overweighting of the issue could sink him. Millions of the suburban voters he needs in battleground states have jobs connected to a strong global trading system. They don’t want to vote for Hillary, but past some point, the “Nafta” rant may prove too much.

So it’s back to the mosh pit. Yankee fans, from the boxes to the bleachers, love their team. But if a guy underperforms or dogs it, they’ll boo him mercilessly. Donald Trump survived Monday night. But one more outing like that, and his phenomenal candidacy could get booed off the field.