Political parties are civic institutions. They are broad coalitions built for the purpose of creating a governing majority that can be used to win elections and pass agendas. This summer three American politicians have risen to the fore, and they all sit outside or at the margin of the party they are trying to lead.

Donald Trump didn’t even swear allegiance to his party’s eventual nominee until last week. He is a lone individual whose main cause and argument is Himself.

Ben Carson has no history in politics and a short history in the Republican Party. He is a politically unattached figure whose primary lifetime loyalty has been to the field of medicine.

Bernie Sanders is a socialist independent, who in the Senate caucuses with the Democrats.

And yet, these anti-party figures are surging in the party races for the presidential nominations.

This phenomenon is even more extreme in Britain. The British Labour Party suffered a crushing election defeat in May because people did not think its leader was strong enough, and because they thought its policy agenda was too far left.

And yet at the moment the favorite to become the next leader of the British Labour Party is Jeremy Corbyn. Mr. Corbyn has existed for decades on the leftward fringe of the Labour Party, tolerated as sort of a nice but dotty uncle.

He spent much of his career at the edge of the parliamentary party, writing columns for The Morning Star, a communist-founded newspaper. He’s a pacifist who called for British withdrawal from NATO. He’s spent his career consorting with the usual litany of anti-Western figures, including his friends in Hamas and Hezbollah. Until about three months ago he was considered the most outside of the outsiders . until a cult of personality developed around him, rocketing him to the top of the polls.

These four anti-party men have little experience in the profession of governing. They have no plausible path toward winning 50.1 percent of the vote in any national election. They have no prospect of forming a majority coalition that can enact their policies.

These sudden stars are not really about governing. They are tools for their supporters’ self-expression. They allow supporters to make a statement, demand respect or express anger or resentment. Sarah Palin was a pioneer in seeing politics not as a path to governance but as an expression of her followers’ id.

Why has this type risen so suddenly?First, political parties, like institutions across society, are accorded less respect than in decades past. But we’re also seeing the political effects of a broader culture shift, the rise of what sociologists call expressive individualism.

There has always been a tension between self and society. Americans have always wanted to remain true to individual consciousness, but they also knew they were citizens, members of a joint national project, tied to one another by bonds as deep as the bonds of marriage and community.

As much as they might differ, there was some responsibility to maintain coalitions with people unlike themselves. That meant maintaining conversations and relationships, tolerating difference, living with dialectics and working with opposites. The Democratic Party was once an illogical coalition between Northeastern progressives and Southern evangelicals. The G.O.P. was an alliance between business and the farm belt.

But in the ethos of expressive individualism, individual authenticity is the supreme value. Compromise and coalition-building is regarded as a dirty and tainted activity. People congregate in segregated cultural and ideological bubbles and convince themselves that the purest example of their type could actually win.

The young British left forms a temporary cult of personality around Jeremy Corbyn. The alienated right forms serial cults around Glenn Beck, Herman Cain, Palin, Trump and Carson.

These cults never last because there is no institutional infrastructure. But along the way the civic institutions that actually could mobilize broad coalitions . the parties . get dismissed and gutted. Without these broad coalition parties, the country is ungovernable and cynicism ratchets up even further.

Maybe this is a summer squall and voters will get interested in the more traditional party candidates come autumn, the ones who can actually win majorities and govern. But institutional decay is real, and it’s what happens in a country in which people would rather live in solipsistic bubbles than build relationships across differences.

I wonder what would happen if a sensible Donald Trump appeared . a former cabinet secretary or somebody who could express the disgust for the political system many people feel, but who instead of adding to the cycle of cynicism, channeled it into citizenship, into the notion that we are still one people, compelled by love of country to live with one another, and charged with the responsibility to make the compromises, build the coalitions, practice messy politics and sustain the institutions that throughout history have made national greatness possible.