Marco Rubio is set to win the latest contest in the battle to be the Republican presidential candidate, a day after being urged to quit the race.
With more than a quarter of votes counted, Rubio has nearly 75% of the vote in Puerto Rico.
Despite his projected second victory in the state-by-state contest, Rubio still trails Donald Trump and Ted Cruz.
On Saturday Mr Trump called for a “one-on-one” battle with Cruz, urging other rivals to quit the race.
In the Democratic race, Bernie Sanders and Hillary Clinton are awaiting the outcome of a nominating contest in Maine, and preparing for a Sunday night debate in Flint, Michigan.
Speaking after wins in the Republican Kentucky caucuses and Louisiana primary election on Saturday, Mr Trump told a news conference: “I would love to take on Ted Cruz one on one.”
“Marco Rubio had a very very bad night and personally I call for him to drop out of the race. I think it’s time now that he dropped out of the race. I really think so.”
Meanwhile, Texas Senator Mr Cruz – who won Republican caucuses in Kansas and Maine – said he believed that “as long as the field remains divided, it gives Donald an advantage”.
While the win in Puerto Rico – a US territory – will boost Rubio’s campaign, it sends just 23 delegates to the Republican convention which nominates a presidential candidate. Republican hopefuls need the votes of 1,237 delegates to get the nod for the presidential race proper.
Races at a glance:
- Donald Trump won two more states on Saturday, bringing his total to 12
- Ted Cruz’s two victories give him six wins in all
- Marco Rubio has now won two states, while John Kasich has none
- Hillary Clinton’s win in Louisiana on Saturday gives her a total of 11 states
- Bernie Sanders’ two victories give him seven wins in all
Election calendar: Next races
- 8 March: Michigan and Mississippi primaries: Democratic and Republican; Hawaii and Idaho caucuses: Republican
- 15 March: Florida, Illinois, Missouri, North Carolina, Ohio primaries: all Democratic and Republican