BEIRUT, Lebanon — Mohammad Rizk sat glumly in his sandwich shop on Wednesday, waiting for customers. The scent of roasting chicken mingled with the fumes of a trash pile just outside. The garbage heap, which seemed to have taken on a life of its own, now dominated the curb where his drive-by clients once idled.

Mr. Rizk, 39, has a degree in economics. Yet without clout in any of Lebanon’s sect-based political parties, he said, he could not get a job in that field, and found himself slinging shawarma in a hot hole-in-the-wall. It was a lot he accepted until this summer, when political gridlock halted trash collection, a relatively reliable public service in a country with precious few of them, and sent protesters into the streets.

“Enough. This is enough,” said Mr. Rizk, declaring that he would join the demonstrators if only he could afford to leave the shop. “No electricity — we said, O.K. No water — we said, O.K. But the trash?”

The mounting garbage piles are one indignity too far, the ultimate physical manifestation of a failed political system that has left the state unable to perform even the most basic functions — so goes the central complaint of the demonstrators, who call their movement “You Stink.”