HONG KONG—Four years ago, millions of voters streamed to the polls in Hong Kong, riding a wave of political anger after months of failed antigovernment protests to give a landslide victory for pro-democracy candidates in district elections.

On Sunday, with elections now engineered to allow only pro-Beijing candidates, the torrent became more of a trickle. The city saw its worst turnout on record as a little more than a quarter of the city’s registered voters went to cast a vote. More than 70% voted at the last district poll in 2019.