Bernie Sanders and Hillary Clinton argued over a number of things in Thursday night's debate, from the legacy of Henry Kissinger to their support for the policies of Barack Obama. On several other issues, they largely agreed with each other. But seldom has the fundamental difference between their conceptions of politics in general, and Democratic politics in particular, been as effectively revealed as it was on the stage in Milwaukee.
For Sanders, the solution to nearly every domestic policy challenge resides in reforming the campaign finance system and restricting the influence of wealthy and corporate interests. Even ostensibly non-economic issues like drug abuse and criminal justice are, for Sanders, closely connected to capitalist exploitation. Clinton implicitly criticized him as a "single-issue candidate" in her closing statement, but it's more accurate to characterize Sanders—at least on domestic policy—as a candidate who cares about many issues but views them as manifestations of a common root cause.
While she has responded to Sanders's rise by insisting that she, too, is dedicated to regulating campaign money and taking on Wall Street, Clinton rejects the claim that these measures will effectively address other social problems, as she stated explicitly in the final moments of the debate:
Yes, does Wall Street and big financial interests, along with drug companies, insurance companies, big oil, all of it, have too much influence? You’re right. But if we were to stop that tomorrow, we would still have the indifference, the negligence that we saw in Flint. We would still have racism holding people back. We would still have sexism preventing women from getting equal pay. We would still have LGBT people who get married on Saturday and get fired on Monday. And we would still have governors like Scott Walker and others trying to rip out the heart of the middle class by making it impossible to organize and stand up for better wages and working conditions. So I’m going to keep talking about tearing down all the barriers that stand in the way of Americans fulfilling their potential, because I don’t think our country can live up to its potential unless we give a chance to every single American to live up to theirs.
There is strategy at work here: Clinton is assuming that African-Americans, Latinos, feminists, union members, gays and lesbians, and other groups under the Democratic big tent do not simply view their own concerns and perceived injustices as limited to, or merely the consequences of, economic unfairness. But there's little reason to believe that her stated views on this particular matter aren't as genuine as are Sanders's, especially since they are consistent with the Democratic Party's traditional coalitional character; Sanders, of course, did not join the Democratic Party until he launched his presidential candidacy last year. (Observers looking for true moments of insincerity during the debate should consider the strong likelihood that both candidates significantly exaggerated the degree of their actual admiration for Barack Obama and his presidential administration.)
Sanders, as he repeatedly suggests, is staking his candidacy on the success of a political revolution. This is commonly understood as a transformational change in the broader electoral environment that would make previously unattainable goals (such as single-payer health insurance) possible. But Sanders is also seeking to redefine the Democratic Party, giving it an ideological nature that it has never previously had in its 200-year history. Clinton, on the other hand, is betting her own ambitions on the same multiplicity of group interests enduring for yet another election.