SAN JUAN, Puerto Rico - Puerto Ricans have supported U.S. statehood in a vote that jubilant members of the pro-statehood party say is the strongest sign yet that the Caribbean island territory is on the road to losing its second-class status.

But Tuesday's vote comes with an asterisk and an imposing political reality: The island remains bitterly divided over its relationship to the United States and many question the validity of this week's referendum.

Nearly a half million voters chose to leave a portion of the ballot blank. And voters also ousted the pro-statehood governor, eliminating one of the main advocates for a cause that would need the approval of the U.S. Congress.

"Statehood won a victory without precedent but it's an artificial victory," said Angel Israel Rivera Ortiz, a political science professor at the University of Puerto Rico. "It reflects a divided and confused electorate that is not clear on where it's going."

President Barack Obama had said he would support the will of the Puerto Rican people on the question of the island's relationship to the U.S., referred to simply on the island as its "status," and this week's referendum was intended to be the barometer.

But the results aren't so clear cut. It was a two-part ballot that first asked all voters if they favor the current status as a U.S. territory. Regardless of the answer, all voters then had the opportunity to choose in the second question from three options: statehood, independence or "sovereign free association," which would grant more autonomy to the island of nearly 4 million people.

More than 900,000 voters, or 54 percent, responded "no" to the first question, saying they were not content with the current status.

On the second question, only about 1.3 million voters made a choice. Of those, nearly 800,000, or 61 percent of those expressing an opinion, chose statehood - the first majority after three previous referendums on the issue over the past 45 years. Some 437,000 backed sovereign free association and 72,560 chose independence. Nearly 500,000, however, left that question blank.

"We made history with this plebiscite," said Resident Commissioner Pedro Pierluisi, the island's representative in Congress and a member of both the pro-statehood New Progressive Party and the Democratic Party.

The certified results will be sent to the White House and the congressional leadership, and it would be up to them to begin the process of possibly admitting Puerto Rico into the union.

"The ball is now in Congress' court and Congress will have to react to this result," Pierluisi said. "This is a clear result that says 'no' to the current status."

Gov. Luis Fortuno, a member of the pro-statehood party who is also a Republican, welcomed the results and said he was hopeful that Congress would take up the cause.

But Fortuno won't be around to lead the fight: Voters turned him out of office after one term, and gave the governship to Alejandro Garcia Padilla of the Popular Democratic Party, which wants Puerto Rico to remain a semi-autonomous U.S. commonwealth.

Garcia has pledged to hold a constitutional assembly in 2014 to address the island's status, followed by another referendum with support from Congress.

Margarita Nolasco, the vice president of the Puerto Rican Senate from the pro-statehood party, said she feared the commonwealth forces would seek to undermine the plebiscite.

"At the beginning of the last century, statehood appeared to be an impossible dream," Nolasco said. "After a century of battles and electoral defeats, statehood just became the political force of majority that Puerto Ricans prefer."

Besides pointing to the defeat of the governor, albeit by a margin of less than 1 percent, skeptics point to other signs that statehood is not ascendant in Puerto Rico.

Luis Delgado Rodriguez, who leads a group that supports sovereign free association, noted all the voters who left the second question blank, raising questions about their preference. He said those voters, coupled with those who support independence and sovereign free association, add up to more than those who favored statehood.

"This represents an overwhelming majority against statehood," he said.

The results are also murky because everyone could vote in the second round no matter how they marked the first question - and the choice of "sovereign free association" is not the same as the current status. So people could have voted for both no change in the first round and any of the choices in the second. Nearly 65,000 left the first question blank.

"With that kind of message, Congress is not going to do anything, and neither is President Obama," Rivera said.

Puerto Rico has been a territory for 114 years and its people have been U.S. citizens since 1917. Residents of the island cannot vote in the U.S. presidential election, have no representation in the Senate and only limited representation in the House of Representatives.

It's a situation that frustrates many, as does the long-simmering political uncertainty. Independence was once the dominant political movement on the island but no longer: Only 6 percent of voters opted to sever ties from the U.S., a prospect that scared voters like 31-year-old Jose Ramos.

"I prefer that the United States helps us, because to stand on our own two feet, no," said the father of three. "I don't want this to become a republic. That scares me."