With 29 percent of the island territory’s districts reporting, former secretary of state Clinton was ahead with 62.5 percent of the vote, compared to 37.1 percent for Sanders, according to CNN.
Victory in debt-hobbled Puerto Rico marked a double dose of good news for Clinton over the weekend, with another territory, the US Virgin Islands, voting overwhelmingly for her on Saturday.
The pair of wins provides a boost ahead of Tuesday’s culminating vote with New Jersey and the big prize of California at stake.
“We just won Puerto Rico! ¡Gracias a la Isla del Encanto por esta victoria!” — she wrote in a bilingual tweet that thanked the Isle of Enchantment for the win.
Puerto Rico has 60 pledged delegates at stake, and Clinton will win at least 31 of them.
That would put Clinton, who amassed 2,323 delegates prior to Puerto Rico’s vote, just a handful shy of the 2,383 needed to clinch the Democratic nomination, a threshold she will undoubtedly cross on Tuesday.
Sanders, however, has vowed to fight on all the way until the Democratic National Convention in July, arguing he could persuade many of the several hundred so-called super delegates who back Clinton to change their allegiance and support his campaign.
Super delegates are Democratic Party bigwigs who are not bound to any candidate or to the results of statewide votes and do not officially cast their vote until the convention.
Both Clinton and Sanders campaigned in Puerto Rico in recent weeks, and both have put forward plans to help the island emerge from a debt crisis.
Lawmakers have introduced legislation, backed by the White House, that would be charged with overseeing fiscal and structural reforms aimed at stabilizing its finances and restructuring the Caribbean island’s $70 billion in debt.