Charles I. Cassell, longtime D.C. Statehood Party leader, was elected president of the D.C. constitutional convention last night, narrowly defeating City Council member Hilda Mason in a 23-21 vote among convention delegates.

Cassell, 57, told the assembly, "I hope we all pull together to write a clear and concise constitution," the first formal step toward statehood for the city.

Delegates also elected seven other officers. The eight constitute the executive committee of the 90-day convention.

Elected first vice president was James W. Baldwin, 57, of Ward 7, former director of the D.C. Human Rights Office and now a personnel consultant. Second vice president is Ward 4 delegate Janette Hoston Harris, a history professor at the University of the District of Columbia. Both Baldwin and Harris are Democratic Party activists. Third vice president is Ward 2 delegate Alexa Freeman, 29, a gay rights activist and a law student at American University.

Elected secretary was Ward 4 delegate William Cooper, 25, a computer consultant and one of only four Republicans among the 45 delegates. Assistant secretary is Ward 1 delegate Richard Bruning, a city Juvenile Court clerk typist and D.C. Statehood Party member. Treasurer is Theresa Jones, a community liaison specialist for the United Planning Organization in Ward 8, and convention historian is Ward 4 delegate Victoria Street, an educational consultant and former D.C. school board member.

The delegation is winding up almost two weeks of preliminary organizing and is expected to move soon to the actual drafting of a constitution.

Once written, the document will go on the ballot, probably in the city's general election this fall. If approved there, a simple majority of both houses of Congress and the president must approve the constitution for statehood to be implemented.

Many city political leaders, including several convention delegates, say the bid for statehood, given the present conservative mood of Congress, is in doubt.