President Clinton wants it. The House of Representatives wants it, by a majority of one. The Senate doesn't want it. And Puerto Ricans aren't sure.

The issue is a referendum that would ask 3.8 million Puerto Ricans whether they want to become our 51st state, opt for full independence or remain a U S. commonwealth, the "half-in, half-out" relationship that has evolved since the Caribbean island was won in the Spanish-American War.But there are many side issues: Language - Do Americans want a Spanish-speaking state? Do Puerto Ricans want to learn English? Cost - Do American taxpayers want to subsidize a state that is twice as poor as the poorest state in the union? Terrorism - Would statehood radicalize Puerto Ricans who want independence and suck us into a "liberation war"?

Spain ruled Puerto Rico for more than four centuries before the United States seized it in 1898. Puerto Ricans were made U.S. citizens in 1917 - the non-voting, non-taxpaying kind - and achieved limited self-governance as a U.S. commonwealth in 1952.

Since then there have been three plebiscites on Puerto Rico's political future, and each time its citizens have chosen to stick with the status quo. The last such vote, in 1993, showed Puerto Ricans almost evenly divided between commonwealth (48.6 percent) and statehood (46.3 percent), with only 4.4 percent opting for independence.

There are advantages to being a commonwealth. Puerto Ricans serve in the U.S. military and enjoy most of the privileges of American citizenship but don't pay federal taxes. Because their annual income averages only $6,500 - less than half that of Mississippi - two-thirds of the population are on some form of welfare, which costs the U.S. government $10 billion a year.

The disadvantage is that they can't vote in U.S. elections and have only one non-voting delegate in Congress.

That delegate, Carlos Romero-Barcelo, is an ardent backer of statehood, saying it would "dismantle 100 years of colonialism" As proof of his second-class status, he points to the fact that he could not vote on the referendum issue when it was debated in Congress earlier this month.

As it turned out, his vote wasn't necessary. The House approved the Puerto Rico Political Status Act 209-208. It calls for a referendum to be held by Dec. 31, 1998, which won't happen if the Senate doesn't concur. And Majority leader Trent Lott says the Senate "won't have time" to tackle Puerto Rico this year.

Even if a referendum does come about, the status of Puerto Rico can only be changed by majority vote, something not achieved in the 1993 balloting. Also, independence or statehood would be preceded by a 10-year transition.

Puerto Rico can't really afford independence, and many lawmakers are not sure the U.S. Treasury can afford Puerto Rican statehood. It is estimated to cost $4 billion a year more than the $10 billion now spent on the island.

Although the House voted down an amendment that would make English the only official language in Puerto Rico, many senators do not want a Spanish-speaking state, fearing it will reopen a divisive controversy about official recognition of second languages in the United States.

Historically, however, Louisiana, New Mexico and Hawaii all had to deal with the language issue and managed to do so without tearing the country apart.

Congressional fears that statehood will turn Puerto Rican separatists into terrorists may be overblown but are not without foundation. The island has suffered periodic bombings - most of them aimed at U.S. interests and limited to property damage - since 1954 when four Puerto Rican "liberation fighters" raked the House floor with gunfire from the gallery, wounding five congressmen.

The leader of that attack, Lolita Lebron, served 25 years in prison before being pardoned by President Jimmy Carter in 1979. Now head of the Puerto Rican Nationalist Party, she says she has "no regrets" and is still fighting for independence but "by peaceful means."