The first is that not all insurgents are created equal: Joe Biden is no Dennis Kucinich. He is the sitting vice president of the United States, which implies access to fundraising networks, campaign talent, and other resources that outsider candidates simply lack. It also lends him a gravitas that hardly anybody else in the party possesses. This is important because the control of the nomination by the party elite is mediated by the party base. Strictly speaking, the voters do indeed determine the nominees under the current system, and the party cannot dictate terms to them. Instead, the elites coordinate their substantial resources to boost their preferred candidate, thus making victory prohibitively difficult for outsiders. Because of his position in the party, Biden should be able to raise enough cash on his own to compete at least in the early states, despite the preponderance of elites going for Clinton. He also has the name recognition and credibility to prompt a close look from Democratic voters.
Historically speaking, vice presidents who run for the White House rarely lose the nomination. In the postwar era, seven sitting or former vice presidents have run for the nomination: Alben Barkley, Richard Nixon, Hubert Humphrey, Walter Mondale, George H.W. Bush, Dan Quayle, and Al Gore. Only Barkley and Quayle failed to secure it. The reason is simple: The office of vice president has a lot of heft. It probably is not enough to overcome the establishment support Clinton enjoys, but the prospect cannot be dismissed out of hand.
Second, the party establishment’s control over the nomination is not a political suicide pact. Granted, Clinton has done a fantastic job of corralling party support early on, but she won’t necessarily hold it over time. The party elites want above all to win, which means Clinton must eventually stop her slide in the general election polls. She already appears to have lost her lead against some of her Republican opponents, and she must remain in striking distance of them. If she cannot do that, look for the party establishment to reevaluate its support, especially if Biden is running stronger in head-to-head matchups against the GOP. It is here that heavy reliance on endorsement data might paint a false picture: The party establishment might start to break away from Clinton behind the scenes before anyone publicly revoked a single endorsement.