Jeb Bush's problem is Jeb Bush

Bush’s net favorability has dropped 28 percentage points since mid-June, while the average candidate’s net favorability declined by just 5 percentage points.

Bush’s falling favorability is, of course, a very bad sign for his candidacy. It suggests that Bush’s fall in the horse-race polls isn’t merely due to other candidates doing better. Instead, Bush seems to be doing worse. Put another way, the more Republican voters get to know Bush, the less they seem to like him. Attacking other candidates, such as when Bush went after Marco Rubio on Wednesday night, is unlikely to solve Bush’s problem.

Right now, Bush’s net favorability, per YouGov, is better than just two other candidates who appeared in the main-stage debate: Chris Christie and Rand Paul. It’s worse than Trump’s, whose net favorability is far below what we’d expect of a future nominee based on his high name recognition.1