WASHINGTON—Six months into office, President Biden has been slow to define his Cuba policy, making no substantial moves to ease his predecessor’s crackdown on travel and remittances, but not repudiating former President Barack Obama’s rapprochement either.

Now, the widespread street protests and the communist government’s violent crackdown may have forced the issue and Mr. Biden faces a challenging political landscape.

“It demands a presidential commitment one way or another. I don’t believe he’ll have the luxury of letting itself play out without his intervention,” said Fernand Amandi, a Miami-based Democratic pollster.

As protests continued Monday, Mr. Biden said: “The United States stands firmly with the people of Cuba as they assert their universal rights. And we call on the government of Cuba to refrain from violence in their attempt to silence the voices of the people.” He added he would have more to say this week.

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Videos show thousands of Cubans protesting food and medicine shortages and calling for the end of dictatorship, in a rare show of dissent. An uptick in coronavirus cases and a slow vaccine rollout are adding to the island’s worst economic crisis in decades. Photo: Stringer/Reuters The Wall Street Journal Interactive Edition

The president’s foreign policy agenda thus far has been consumed with countering China and Russia and re-engaging European allies. Former President Donald Trump’s gains among Cuban-American voters in Florida in 2020 have demonstrated the domestic political peril of outreach to Havana, political analysts say.

After the Obama administration restored diplomatic relations with Havana and loosened longstanding travel and financial restrictions, Mr. Trump reversed course. One of his final acts in January was to return Cuba to the list of countries considered state sponsors of terrorism.

In April when Raúl Castro said he was stepping down as head of the Communist Party, White House spokeswoman Jen Psaki said, “A Cuba policy shift or additional steps is currently not among the president’s top foreign policy priorities.”

Raul Castro, wearing glasses, raised the hand of Cuban President Miguel Diaz-Canel after the president was elected first secretary of the Communist Party in April.

Raul Castro, wearing glasses, raised the hand of Cuban President Miguel Diaz-Canel after the president was elected first secretary of the Communist Party in April.

Photo: Ariel Ley Royero/Associated Press

On Monday, she said, “I don’t have anything to predict for you in terms of any policy shift,” adding the U.S. is looking at how it can support the demonstrators, including through humanitarian aid.

The State Department has said recently that its review of Cuba policy was ongoing. Department officials didn’t immediately respond to requests for comment on the protests or their effect on U.S. policy.

While campaigning last year in Florida, home to a large contingent of Cuban-American voters, Mr. Biden said his predecessor’s Cuba policy wasn’t working. “Cuba is no closer to freedom and democracy today than it was four years ago,” Mr. Biden said in October. “In fact, there are more political prisoners. The secret police are as brutal as ever, and Russia is once again a major presence in Havana.”

Among the changes the administration is considering is loosening travel between the two countries and permitting Cubans in the U.S. to send more money to family on the island.

In November Mr. Trump won Florida by 3.3 percentage points, improving on his narrow 2016 victory, in part by strength in South Florida. During the campaign the Republican Party sought to portray the rising liberal wing of the Democratic Party as socialist, a message that ultimately resonated with Cuban Americans, Venezuelans and other voters who fled leftist governments.

Some Democrats blamed the Biden campaign for not doing enough to combat that messaging, and it remains a concern ahead of the midterm elections. Democrats hold slim majorities in both chambers of Congress. In Florida, the largest battleground state, Democrats lost two Miami congressional seats to Republicans in 2020.

Government protesters in the streets of Havana on Sunday.

Government protesters in the streets of Havana on Sunday.

Photo: alexandre meneghini/Reuters

“The bottom line is that the lobbying group for opening Cuba is now in a weak position,” said Jorge Duany, director of the Cuban Research Institute at Florida International University.

He cited several developments, including the rise of Sen. Robert Menendez (D., N.J.) as chairman of the Foreign Relations Committee. Mr. Menendez advised Mr. Biden during the campaign against reverting to Obama policies, while other Democrats pushed to undo Mr. Trump’s actions, arguing as did Mr. Biden that they didn’t affect change on the island.

Mr. Menendez, appearing Monday afternoon on CNN, said he thinks the new administration concluded Mr. Obama’s approach didn’t work.

“I think the president has had time to review the actual policies under President Obama and all of the openings President Obama made, which were one-sided, unilateral in terms of concessions, showed themselves to create absolutely no change inside of Cuba,” he said.

The senator said he has provided the White House with a list of policy recommendations. His office declined to share that list.

Another factor is a continuing investigation into possible sonic attacks U.S. diplomats have suffered in Havana, which has led to a sharp reduction of embassy staff. Cuba has denied wrongdoing.

Mr. Amandi said the Biden administration has been rightly reluctant to make changes to Cuba policy since the government there hasn’t lived up to the promises made with Mr. Obama. But he said the current crisis is an opportunity.

“The developments of the last 48 hours should make him seize the moment both for policy and political reasons,” Mr. Amandi said. “The most effective way to end the charge that Democrats are socialists is to preside over the liberation of Cuba.”

Republicans plan to keep up the pressure on Mr. Biden. Florida Republican Sen. Marco Rubio, who is up for re-election in 2022, warned Monday that the Cuban regime could threaten to send waves of Cubans to the U.S., as happened with the 1980 Mariel boatlift.

“We must not cave to blackmail & [President Biden] must warn them that encouraging mass migration will be considered a hostile action,” Mr. Rubio wrote on Twitter.

—Courtney McBride and Tarini Parti contributed to this article.

Write to Alex Leary at alex.leary@wsj.com