The very status of such parties as insurgents and rebels reflects their dilemma: By positioning themselves as outsiders, they exclude themselves from the mainstream, which they anyhow revile or mock as emblems of a corrupt and elite establishment that has failed the people.

That, in turn, deepens their vulnerability to the inherent frailty and short shelf life of narrow, issue-driven politics. Indeed, the failure of many to build the kind of political machines that determine Western elections leaves their leaders dependent on sometimes troublesome lieutenants and exposed to squabbles within their ranks.

In Britain, Nigel Farage, the beer-drinking, one-of-the-lads leader of UKIP, has tangled frequently with rambunctious figures in his own party, most recently last week, when one of them, Godfrey Bloom, was suspended after referring to women as “sluts” and using a copy of the party’s political program to beat a television reporter over the head, on camera.

Even Mr. Farage admitted that the episode on the fringes of the party’s autumn conference had been a huge setback. “We can’t have any one individual, however fun or flamboyant or entertaining or amusing they are, destroying UKIP’s national conference and that is what he has done,” Mr. Farage said of his erstwhile ally.

It is no coincidence that such populist tub-thumping parties — often anti-immigrant and conservative, but by no means limited to the far right — have seized headlines as Europe’s economic crisis has bitten deeply not only into pocketbooks but also into the reputation of the political elite.

The range of contenders embraces Geert Wilders’s Freedom Party in the Netherlands as much as parties on the left and right in Greece, including the neo-fascist Golden Dawn.

The insurgents’ record for durability is mixed. Some, like the Greens in Germany, or the more established National Front of Marine Le Pen in France, which long predates the latest wave of start-up rebels, have settled into the political spectrum. Others, like Germany’s Pirates, whose main issue is Internet freedom, have fizzled.