One congressman after another addressed the crowd assembled on the Capitol's steps yesterday, denouncing Phillippine President Ferdinand Marcos and his wife Imelda, calling for curtailment of military aid to his government and demanding an end to the martial law that he imposed on his country exactly six years ago.

"Mabuhay! Mabuhay!" shouted the crowd in Tagalog, the Philippine language. "Long Life."

They have come to Washington - 250 delegates to the convention of the Movement for a Free Philippines - from all over the United States. Some were born in America, some came after fighting alongside American soldiers during World War II, and many others have come in recent years to escape the oppression they say they feel under the Marcos regime.

All appeared committed to the idea expressed by the movement's president, Raul S. Manglapus, that "the peculiar love-hate relationship between the Philippines and America" has ultimately instilled in the Filipinos a powerful desire for democracy and political freedom now thwarted by Marcos.

"I think it is sad that a people who fought for freedom in war," said Sen. Birch Bayh (D-Ind)., "should be denied that freedom in peace."

Sen. Edward M. Kennedy (D-Mass) told the Filipinos who talked with him in his office that they were welcome in Washington as they sought "the restoration of democracy in the Philippines."

Manglapus said his organization hopes to encourage such sympathetic senators and representatives, who were given certificates of appreciation yesterday and to persuade others to vote to withdraw military aid from the Marcos regime. Without that aid, said Manglapus, Marcos' government would fall and could be replaced by a working democracy.

Manglapus - a former Philippine foreign minister and senator now living in McLean - said he believed Marcos would not dare close U.S. bases in his country, because he needs them almost as much to shore up his political image as the U.S. needs them militarily.

A U.S. State Department official familiar with the situation called this estimate "highly speculative."

U.S. Immigration and Naturalization statistics show that more than 200,000 immigration from the Philippines have come into the U.S. since martial law was imposed by Marcos in 1972. An INS spokesman said it is difficult to tell just how many have come specifically to escape the Marcos regime.