MOSCOW—Russia’s ruling United Russia party, which supports President Vladimir Putin, retained its majority in parliament after a three-day election and a sweeping crackdown on its critics, despite losing around one fifth of its support, partial results on Monday showed. With 33 percent of ballots counted, the Central Election Commission said United Russia had won just over 45 percent of the vote, with its nearest rival, the Communist Party, at around 22 percent. Although that amounts to an emphatic win, it would be a weaker performance for United Russia than the last time a parliamentary election was held in 2016, when the party won just over 54 percent of the vote. A malaise over years of faltering living standards and allegations of corruption from jailed Kremlin critic Alexei Navalny have drained some support, and a tactical voting campaign organized by Navalny’s allies appears to have inflicted further damage. Kremlin critics said …