The district councils are among the most democratic bodies in Hong Kong. Almost all the seats are directly elected, unlike the legislature, where the proportion is just over half. The territory’s chief executive is also not chosen directly by voters, but is instead selected by a committee stacked in favor of Beijing .

The election results will give democracy forces considerably more influence on that committee , which is scheduled to choose a new chief executive in 2022.

The district councils name about a tenth of the group's 1,200 members, and now all of these will flip from pro-Beijing to pro-democracy seats. Democracy advocates already control about a quarter of the seats, while other previously pro-Beijing sectors of the committee are now starting to lean toward democracy, most notably accountants and real estate lawyers.

Mr. Leong, the Civic Party chairman, called on the Chinese Communist Party to change its policies in Hong Kong.

“Unless the C.C.P. is doing something concrete to address the concerns of the Hong Kong people,” he said, “I think this movement cannot end.”

Regina Ip, a cabinet member and the leader of a pro-Beijing political party, said she was surprised to see so many young voters, many of whom tried to confront her with the protesters’ demands.