Republican presidential candidate Donald Trump came under intense scrutiny Thursday for allegations that he knowingly violated the U.S. embargo on Cuba in the 1990s, a report that could hurt him among Cuban Americans in the crucial state of Florida.

A story published in Newsweek said Trump’s firm spent as much as $68,000 on a “foray” exploring business possibilities in Cuba in 1998, which would be a clear violation of the strict embargo in place at the time.

Trump spokeswoman Kellyanne Conway suggested in a television interview Wednesday that Trump had indeed spent money exploring business ventures in Cuba. But Conway later told The Washington Post that she “did not say he broke the law or violated the embargo.”

Trump himself denied the allegations during an interview in New Hampshire, where he campaigned Thursday, and sought to discredit the reporter who wrote the story.

“I never did business in Cuba. There’s this guy who has a very bad reputation as a reporter. You see what his record is. He wrote something about me in Cuba. No, I never did anything in Cuba. I never did a deal in Cuba,” he told NH1 News. 

President Obama, right, and his Cuban counterpart, Raul Castro, wave to cheering fans as they arrive for a baseball game between the Tampa Bay Rays and the Cuban national baseball team in Havana on March 22, 2016. (Rebecca Blackwell/AP)

The report could become a significant political liability for Trump among Cuban Americans in Florida, a key battleground state in his fight against Democratic rival Hillary Clinton. The two candidates are in a virtual dead heat in the state, according to the RealClearPolitics polling average.

Susan MacManus, a nonpartisan Florida political analyst, said the issue could cause great concern among older Cuban Americans in the state, who are firmly pro-embargo. Those voters have expressed disdain for the Obama administration’s decision to open relations with Cuba.

“The hard-liners in the Cuban community are very high-turnout voters. And they’re shrinking in number,” she said. “Trump just went down there and had a special meeting with these people to try to shore up support with them. And, so, just when Trump was making inroads and assuring that community that he was on their side, then this story comes out.”

Ana Navarro, a Florida-based conservative strategist opposed to Trump, said that “it is never a good thing when voters feel played and find out the candidate they are supporting is a hypocrite on an issue that carries the emotion that Cuba policy does.”

Sen. Marco Rubio (R-Fla.), a former primary challenger of Trump’s who is running for reelection in November, urged the Trump campaign to address questions about the case but said he would not comment further until more information is known.

“The article makes some very serious and troubling allegations. I will reserve judgment until we know all the facts and Donald has been given the opportunity to respond,” Rubio said in a statement.

According to Newsweek, the fees associated with a business trip to the island by Trump representatives were paid by Trump Hotels and Casino Resorts through a consulting firm called Seven Arrows Investment and Development. The consulting firm later said the trip had been taken on behalf of a Catholic charity.

Trump blasted President Obama for a “one-sided deal for Cuba” this month during a campaign event in Florida. He said the move to normalize relations would benefit the Castro regime. He has vowed to reverse Obama’s efforts to open U.S.-Cuba relations if he is elected president, “unless the Castro regime meets our demands — not my demands, our demands.”

Clinton told reporters aboard her plane that Trump’s business exploration in Cuba “appears to violate U.S. law, certainly flout American foreign policy, and he has consistently misled people in responding to questions about whether he was attempting to do business in Cuba.”

“This adds to the long list of actions and statements that raise doubts about his temperament and qualification to be president,” she added.

Conway, during a tense appearance on ABC’s “The View,” appeared to say that Trump had spent money in Cuba but emphasized that “he decided not to invest there.”

“I think they paid money, as I understand from the story, in 1998 — and we’re not supposed to talk about years ago when it comes to the Clintons,” Conway said amid cross-talk.

“So the question is: Did he spend money? He’s very critical of Cuba, he’s very critical of Castro, he’s been critical of Cuba,” she said. “He gave a speech the very next year to the Cuban American National Foundation in Miami critical of those who want to do business with Castro.”

In that 1999 speech, Trump denounced the Castro regime.

“I’ve had a lot of offers and sadly it’s all been very recently to go into Cuba on deals, business deals, real estate and other deals. And I’ve rejected them on the basis that I will go when Cuba is free,” Trump said at the time, according to a video of his remarks. “Putting money and investing money in Cuba right now doesn’t go to the people of Cuba. It goes into the pockets of Fidel Castro. He’s a murderer, he’s a killer, he’s a bad guy in every respect.”

Conway said several times Thursday that Trump did not ultimately invest money on the island and sought to focus attention on foreign donations to Bill and Hillary Clinton’s family foundation.

“But again, we’re talking about, did his hotel invest money in 1998 in Cuba? No. Did she get money from seven foreign governments while she was secretary of state? Yes.”

Sean Sullivan, Ed O’Keefe and Anne Gearan contributed to this report.