HONG KONG — A group of young people committed to rewriting the rules that govern Hong Kong’s relationship with China were swept into office on Sunday in elections for the city’s legislature, lifted by record voter turnout, according to a government vote tally.

Some of the young protesters who took part in Hong Kong’s enormous 2014 pro-democracy demonstrations will now wield a small measure of real political power for the first time.

The failure of that movement to secure major democratic reforms in Hong Kong, a former British colony, and fears that the city’s considerable autonomy was under assault led these candidates to campaign on everything from self-determination to the outright independence of Hong Kong from mainland China.

Their success signals the emergence of a new political force. Until now, the pro-democracy forces in the city have been dominated by politicians who sought to expand the power of voters to select the city’s leaders and lawmakers under the guidance of the mini-constitution that codifies Hong Kong’s special relationship with mainland China, called “one country, two systems.”