Anyone who has lived in a dysfunctional or struggling democracy knows that a politics of enmity can end in rule by presidential decree, or even in political violence. Americans consider such scenarios unthinkable. Yet even if the standoff over the debt ceiling ends in a deal, it will already have exacted a brutal price. Extremists will come away believing that hostage-taking might work next time. When blackmail becomes standard practice, democracy is pulled a step closer to permanent paralysis.

Some experts believe that the enmity mind-set simply reflects real divisions in the society at large. Inequalities in income, wealth and opportunity have soared, the argument goes, making it impossible for ordinary Americans to respect each other as adversaries.

Other thoughtful observers argue — I think convincingly — that while factions at either end of the political spectrum do see each other as enemies, most Americans are actually not as divided as their politics makes them seem. The real problem, in this account, is the political system: districts drawn so that incumbents never face the challenge of reaching out beyond their own base; primary systems that reward extremist activists over moderate pragmatists; campaign finance rules that allow big, opaque donations by wealthy interests.

From this perspective, the politicians aren’t so much reflecting the divisions in American society as they are exacerbating them, from the top down.

The tendency is to magnify differences of policy into differences of conviction. For example, Republican and Democrat voters alike are ever more dependent on government programs like Social Security and Medicare, but you would never know this from the way Tea Party Republicans describe Obamacare as an assault on freedom.

Politicians ratchet up manageable differences of policy into conflicts over identity and value. In this way, what Freud called the “narcissism of minor differences” drives party activists into closed worlds of discourse, while leaving the rest of Americans feeling that “the system” fails to serve them at all. They cease participating altogether, leaving the politicians to brawl in a deserted public square.

Besides magnifying differences, the politics of enmity makes competition viscerally personal. The object is not to rebut what people say, but to deny them the right to be heard at all. Attack ads that deny standing have been a feature of American politics from Lyndon B. Johnson’s depiction of Barry M. Goldwater as mentally unstable menace to the “swift boating” of John F. Kerry. The politics of personal destruction have come to seem normal, even acceptable.