“We have gone through two World Wars, the Great Depression, the Cuban trade embargo, smoking bans, excessive taxation and competition from low-wage countries,” said Eric Newman, who with his brother Bobby, owns and operates the country’s oldest premium cigar business, founded in 1895 in Cleveland by his grandfather Julius Caeser Newman. “The toughest challenge of all these is the F.D.A. regulations.”

If the factory closes, Tampa would lose its most historic link to the city’s 128-year-old cigar legacy, a blow that many agree would be deeply felt. It is not hard to see why. Inside El Reloj, cigar workers, most of them women, sit behind 1930s-era machines and lay a long tobacco leaf on a metal plate, cutting it before it slides off to be rolled. In another room, women push pedals on machines from the 1910s that strip the stem from the leaf (the women are indelicately called strippers). The process has not changed since the 1930s when Mr. Newman’s grandfather bought his first set of machines; two decades later he moved his cigar factory to Ybor City from Cleveland.

The factory is dominated by rooms with broad windows facing north and south, and its original floors, barrels, ceilings and smells make it easy to reel back the decades to a time when immigrants from Cuba and Spain rolled cigars by hand to the voice of a lector reading from a book or newspaper to entertain them.

All of that is now at risk.

In keeping with a 2009 law granting the F.D.A. more regulatory power over tobacco products, the agency is proposing to oversee additional products including cigars and e-cigarettes. The aim is to regulate cigars as the government does cigarettes to try to discourage minors (and people, in general) from buying them in places like convenience stores and acquiring the habit, which can increase the risk of some cancers. “Tobacco remains the leading cause of death and disease in this country,” the F.D.A. commissioner, Margaret A. Hamburg, said in the agency’s announcement of the proposed new rules.

Two proposals are on the table and both would hurt the factory’s prospects, Eric Newman said. The proposals are still open to public comment until early August, at which point the agency will begin to finalize the rules.