Senator Marco Rubio’s victory in Puerto Rico could help him in Florida primary

Senator Marco Rubio of Florida won the Puerto Rico primary on Sunday, giving him a much-needed victory after a string of losses that threatened to push the Republican presidential nomination further out of his reach.

In Maine on Sunday, Senator Bernie Sanders won the Democratic caucuses, according to The Associated Press.

The victory in Puerto Rico came a day after Mr. Rubio was shut out of first-place finishes in all four of Saturday’s Republican nominating contests, where Senator Ted Cruz of Texas won the caucuses in Kansas and Maine, and Donald J. Trump won the Kentucky caucuses and the Louisiana primary.

Saturday’s results helped Mr. Cruz emerge as the main alternative for Republicans hoping to halt Mr. Trump’s momentum. Mr. Cruz has now beaten Mr. Trump, who holds the lead in delegates, in six states. Mr. Rubio’s lone previous victory came in the Minnesota caucuses.

Mr. Rubio — who in recent days has focused on his home state, which he must win in its March 15 primary if he hopes to continue his campaign — made a detour to Puerto Rico on Saturday, campaigning in San Juan and holding a news conference, mostly in Spanish, in a last-minute push to win the primary.

Puerto Rico, which has roughly 3.7 million residents, could help Mr. Rubio in his home state’s primary. More than one million Puerto Ricans live in Florida, concentrated most heavily around Orlando, and many were closely watching their island’s contest Sunday.

Puerto Rico is embroiled in a debt crisis, with the territory facing a deficit of more than $70 billion. Mr. Rubio took a tough line on the matter in Congress, urging Puerto Rico to focus on improving its economy and fixing its troubled fiscal situation rather than seeking bankruptcy protection.

Mr. Sanders’s win in Maine was his third of the weekend, and he assured supporters he still had “a path toward victory” and urged the media not to “write us off.”

It came a day after he won the caucuses in both Kansas and Nebraska on Saturday. But Hillary Clinton, his Democratic rival, also notched a decisive victory on Saturday, beating him in the Louisiana primary — which allowed her to amass more delegates over all on Saturday and continue to expand her delegate lead.

On Tuesday, Michigan will hold its primary, a critical test for both Mrs. Clinton and Mr. Sanders as the nominating contests incorporate Rust Belt states. On Sunday night, the Democratic debate was held in Flint, Mich., where the water crisis was the primary focus.

Mrs. Clinton on Friday campaigned in Detroit, laying out her job growth plan, which includes providing incentives for employers to that invest in the United States and “clawing back” tax incentives from companies that move their business overseas.

And for Mr. Sanders, Michigan — with its working-class white voters who should be receptive to his populist message — is the sort of state he needs to win to remain viable and prove he can beat Mrs. Clinton, who decimated him in the South with the strong backing of African-American voters.