Puerto Ricans were facing a fundamental question on Election Day: Should they change their ties with the United States?

Citizens in the U.S. island territory cannot vote in the U.S. presidential election, but many were excited to participate in a referendum that could help determine the island's political future, pushing it toward statehood, greater autonomy or independence.

Car horns blared and party flags waved as voters headed to polling stations, some of them yelling their political preferences. Many carried umbrellas to shield themselves from a blistering tropical sun as temperatures neared 31 degrees Celsius.

Statehood, independence, or 'sovereign free association'

The two-part referendum first asks voters if they want to change Puerto Rico's 114-year relationship with the United States.

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A boy waves a national flag during the Popular Democratic Party campaign's closing rally in San Juan. (Ana Martinez/Reuters)

A second question gives voters three alternatives if they do want a change: become the 51st U.S. state, independence, or "sovereign free association," a designation that would give more autonomy for the territory of 4 million people.

"Puerto Rico has to be a state. There is no other option," said 25-year-old Jerome Lefebre, who picked up his grandfather before driving to the polls. "We're doing OK, but we could do better. We would receive more benefits, a lot more financial help. Let's finish what we started."

But 42-year-old Ramon Lopez de Azua said he favours the current system, which grants U.S. citizenship but prevents Puerto Ricans from voting for U.S. president and gives the island only limited representation in Congress.

"Puerto Rico's problem is not its political status," he said. "I think that the United States is the best country in the world, but I am Puerto Rican first."

Statehood could grant $20 billion a year

Both President Barack Obama and presidential candidate Mitt Romney have said they supported the referendum, with Obama pledging to respect the will of the people if there is a clear majority. Any change would require approval by the U.S. Congress.

The island also is electing legislators and a governor, with Gov. Luis Fortuno of the pro-statehood New Progressive Party seeking a second term. Fortuno, a Republican, is running against Alejandro Garcia Padilla, whose Popular Democratic Party favours the status quo.

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Puerto Rico's Governor Luis Fortuno of his pro-statehood New Progressive Party is greeted by a supporter after casting his vote in San Juan. (Ana Martinez/Reuters)

Pro-statehooders say Puerto Rico would benefit from becoming a state because it would receive an additional $20 billion a year in federal funds to boost the local economy and fight crime. The island currently has a higher unemployment rate than any U.S. state at 13.6 per cent, and last year it reported a record 1,117 killings.

A status of sovereign free association, meanwhile, would award Puerto Rico more autonomy and allow U.S. jurisdiction only in certain judicial matters. The details of the relationship would have to be agreed upon by the U.S. and Puerto Rican governments.

Independence, the unlikely third choice

A third choice, outright independence, has received little support in the last couple of decades.

At a small university in historic Old San Juan, balloting moved slowly, a line of voters snaking out the door and into a sunbaked plaza.

Manolo Nunez Negron, a 31-year-old literature professor, was annoyed at the wait but said he was excited to vote for a change of governor.

"Puerto Rico is deciding if it will continue supporting Republican policies that have hurt the middle class and the working class," Nunez said after casting his vote.

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Popular Democratic Party gubernatorial candidate Padilla, who favours the island's current political status, speaks to followers during the party campaign's closing rally in San Juan. (Ana Martinez/Reuters)

Nilda Rodriguez, a "40-something" nurse, said she was supporting statehood and Fortuno as governor, mostly because she wants Puerto Rico to be more like the United States, where she believes the government is more efficient and responsive.

"We've had the same status all these years and it needs to change," Rodriguez said as she headed off to work, a pink stethoscope slung over her shoulder. "We're going to see if things get better because it has gone from bad to worse."

Puerto Rico also held non-binding referendums in 1967, 1993 and 1998, with statehood never garnering a clear majority and independence never obtaining more than 5 per cent of the vote.

In a poll this month, local newspaper El Nuevo Dia found that a very slim majority favoured the current political status. On the second question, the preference for statehood topped sovereign free association. Few said they favour independence.