FILE - In this March 21, 2016 file photo, President Barack Obama shakes hands with Cuban President Raul Castro during their meeting at the Palace of the Revolution in Havana, Cuba.

Image Credit: AP Photo/Pablo Martinez Monsivais, File

WASHINGTON - For a few short days, President Barack Obama was America's man in Havana, his challenges to President Raul Castro stunning Cuban citizens who mused openly in the streets about the possibility of political change.

Obama's public call for a more democratic Cuban future marked a watershed moment in a country where questioning the government's authority is not tolerated. Decades of bitterness between leaders seemed to fade as Obama and Castro laughed it up at a baseball game. U.S. businesses were flocking in droves, touting new approval to bring Americans and their dollars to Cuba.

As Obama's aides jubilantly boarded Air Force One, Castro showed up on the tarmac to see Obama off. The White House saw it as an affirmation that the visit was a success, even by Castro's admittedly different standards.

Yet a key question remained unanswered after Obama departed the communist island: How much of it will last?

"We shouldn't kid ourselves that they're going to all of a sudden tolerate dissent," said Michael Posner, Obama's former assistant secretary of state for human rights and democracy. "This is a very ostracized regime. They've been in power a long time. They don't really have any instincts for reform. It's going to be a struggle."

The first clues could come next month during the Communist Party Congress meeting in Havana, a forum for unveiling major changes. An announcement of greater political freedoms or reform-minded economic steps would suggest that Obama's strategy was starting to bear fruit.

Under the glare of global attention, Castro did little to publicly undermine Obama. After all, Obama enjoys immense popularity in Cuba. Images of a young black president strolling through Old Havana seemed to resonate with Cuba's racially diverse people, forming a powerful contrast with the aging Castro.

In the days ahead, though, that public spotlight will dim, giving Castro an opening to return to business as usual should he so choose. Though he's taking modest steps to open up Cuba's economy and relax certain social restrictions, there are still no indications Castro plans to make any of the changes to Cuba's single-party system that Obama advocated.

"We will continue to speak out loudly on the things that we care about," Obama said near the end of his visit.

Central to Obama's strategy is to raise the Cuban people's expectations, driving up pressure on Castro's government to accelerate the pace of change. Wary Cuban officials have picked up on the tactic, with some regarding Obama's entreaties as a post-Cold War attempt to coerce Cuba with diplomacy instead of the threat of force.

Ahead of his trip, Obama's aides said a key goal was to make his rapprochement with Cuba irreversible. He left the island with plenty of indications that tipping point could be in sight.

Soon, as many of 110 commercial flights between the U.S. and Cuba will take off daily, bringing millions of Americans to the country and further exposing Cubans to the outside world. With Americans hungry for a taste of Havana, Obama is banking on the notion that it will be incredibly unpopular for the next president to tell them to cancel their vacations.

Famed U.S. hotel chains Starwood and Marriott are poised to take over hotels in Cuba after striking deals with Havana and getting permission from Washington, and Google is making a major play on the island as well. Brian Chesky, CEO of online lodging service Airbnb, told reporters in Havana that Cuba is his company's fastest-growing market.

"There comes a point where reversing it will seem like a very crazy idea," said former Commerce Secretary Carlos Gutierrez, a Republican who left Cuba as an exile at age six. "I think we're just about at that stage."

Though Obama advanced his goal of normalizing U.S.-Cuba relations, it wasn't without political risk.

His visit was roundly derided by supporters of the U.S. trade embargo, who accused Obama of rewarding a repressive government. It's an issue with resonance in the presidential race, where Republican candidate Ted Cruz, whose father is Cuban, is livid about Obama's policy while front-runner Donald Trump vows to negotiate a better deal.

"Today is a sad day in American history," Cruz said while Obama was in Havana.

Both Democratic candidates, Hillary Clinton and Bernie Sanders, support Obama's approach.

Obama has also been unable to remove the key irritant for Cuban officials and citizens alike: The U.S. embargo, which has squeezed Cuba's economy for generations. There are few signs Congress will accede anytime soon to Obama's calls for repealing the sanctions.

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EDITOR'S NOTE — Josh Lederman has covered the White House for The Associated Press since 2013.

News from © The Associated Press, 2016