Every time you think that our political discourse can’t get any worse, it does. The Republican primary fight has devolved into a race to the bottom, achieving something you might have thought impossible: making George W. Bush look like a beacon of tolerance and statesmanship. But where is all the nastiness coming from?

Well, there’s debate about that — and it’s a debate that is at the heart of the Democratic contest.

Like many people, I’ve described the competition between Hillary Clinton and Bernie Sanders as an argument between competing theories of change, which it is. But underlying that argument is a deeper dispute about what’s wrong with America, what brought us to the state we’re in.

To oversimplify a bit — but only, I think, a bit — the Sanders view is that money is the root of all evil. Or more specifically, the corrupting influence of big money, of the 1 percent and the corporate elite, is the overarching source of the political ugliness we see all around us.

The Clinton view, on the other hand, seems to be that money is the root of some evil, maybe a lot of evil, but it isn’t the whole story. Instead, racism, sexism and other forms of prejudice are powerful forces in their own right. This may not seem like a very big difference — both candidates oppose prejudice, both want to reduce economic inequality. But it matters for political strategy.