President Ferdinand Marcos' proposal for a special presidential election in the Philippines passed another hurdle tonight when the National Assembly approved a bill setting the vote for Feb. 7.

Passage of the bill, which is expected to go to Marcos for signature in several days, came as many analysts here continued to say that legal challenges and political maneuvering may result in the election never taking place.

In today's debate, opposition members of the assembly made three efforts to move the polling date back to give their camp more time to organize. But the assembly, dominated by Marcos' New Society Party, went on to pass the bill 77 to 41.

Opposition members said they would go to the Supreme Court to challenge the legality of the election. They contend it is unconstitutional because Marcos has said he will not leave office before the voting takes place.

The bill provides for a president and vice president to be elected to six-year terms. Candidates must register by Dec. 11, when a 57-day campaign would begin.

Facing pressure from domestic opponents and the U.S. government, Marcos proposed the special election earlier this month. His current term does not expire until 1987.

The Philippines' diverse opposition parties have condemned the election as illegal and at the same time welcomed it as a chance to topple Marcos, who has been in power since 1965.

To date, however, they have been unable to decide on a single ticket to run against him and avoid splitting their vote. The major contenders are former senator Salvador Laurel, head of the country's largest coalition of opposition parties, and Corazon Aquino, widow of assassinated opposition leader Benigno Aquino.

Members of the National Unification Committee, an opposition umbrella group charged with assuring there is a single opposition ticket, called today for a convention to be held not later than Dec. 9 to resolve the ticket question if the opposition is unable to unite behind one challenger.

Marcos' party, meanwhile, is set to meet Dec. 7 to nominate him. The identity of his running mate is a subject of constant speculation, with some sources suggesting he may run with his wife Imelda, who is minister of human settlements and governor of Metro Manila, despite public statements by both to the contrary.

Conflicting statements by Marcos on the mechanics and scope of the election have led many observers here to question his intentions. By some accounts, he wants only to appear to be responding to pressure for a vote and does not want one to take place.

In a meeting with reporters today, Laurel suggested that if he and Aquino were able to reach a deal to run together, Marcos might feel threatened and allow the Supreme Court to nullify the plan as unconstitutional.