Nayib Bukele, the 42-year-old president of El Salvador, won reelection in a landslide, and boasted that the Central American country had established a one-party system via democratic means.

“The entire opposition has been crushed,” he declared Sunday night.

The vote tally was plagued by internet outages and other irregularities; authorities finally resorted to manual counting. With 70 percent of polling stations reporting, Bukele had about 1.6 million votes — more than 10 times as many as his nearest rival, leftist Manuel Flores. An exit poll by CID Gallup found Bukele had won about 87 percent of the vote.