Brian Leiter, who teaches moral, political and legal philosophy at the University of Chicago, has more confidence in Sanders. A commentary he recently wrote for the Huffington Post is titled: "Roosevelt, Reagan and the Sanders Moment."

"No one has a crystal ball about what tomorrow’s consensus will be," Leiter said in an email. "Ronald Reagan was viewed as a wild outlier from the political consensus. He ended up changing it. That’s probably the clearest example of someone thought to be a divisive figure going on, who ended up shifting the entire spectrum of political opinion his way."

A tall comparison for Sanders?

"One reason that Clinton is having so much trouble deflecting Sanders’s challenge is because his main claims about a 'rigged' political system and a 'rigged' economy are pretty obviously true," Leiter said. "Even if one disagrees with his solutions, who with a straight face can deny the problem? That’s why Clinton is in a pickle."

Regardless of the Democratic nominee, St. Louis University political science professor Penny Weiss said consensus is difficult to achieve at a high level because division has become a "principled stance rather than cooperation and compromise."