Why did embracing his party’s establishment work for Biden but not for Bush? Because Democrats like their establishment more. Although progressive activists criticize Obama, his approval rating among Democrats as a whole—according to Real Clear Politics’ polling average—is almost 87 percent. That makes Biden’s association with him an almost unmitigated political strength. By contrast, an internal Bush campaign poll showed that Jeb’s family connections turned many voters off. The “Bush stuff was holding him back,” one aide told The Washington Post.

Obama isn’t just personally more popular among Democrats than George W. Bush was among Republicans. His agenda is more popular too. Eighty-five percent of Democrats approve of Obamacare. By contrast, a May 2015 poll found that only 54 percent of Republicans believed that the Bush administration’s signature initiative—the Iraq War—had been worth fighting…

By the time he left the race, Jeb Bush had a net favorability rating among Republicans of only five points. Biden’s net favorability among Democrats last month, by contrast, was almost 50 points. That discrepancy isn’t simply a function of the two candidates’ performances on the stump. It’s a statement about the party establishments they represent. Asked to explain Bush’s failure, Mike Murphy, the chief strategist for the former governor’s super PAC, explained, “Our theory was to dominate the establishment lane” but “the problem was there was a huge anti-establishment wave. The establishment lane was smaller than we thought it would be.”