The D.C. constitutional convention completed its organizing phase yesterday in a final round of bickering over committee memberships and will begin the formal task of writing a constitution Monday in the city's bid for statehood.

The carefully juggled set of committee assignments and chairmanships for the 45 delegates was nearly dislodged when three delegates switched committees after the heads of two of the committees had already been selected.

Some angry delegates demanded new committee-by-committee elections, threatening to prolong the already delayed convention. But the move was beaten back in a series of procedural votes, and the original committee chairmanships were kept intact.

The result: A scant majority of the 10 committees charged with writing various portions of the constitution are headed by delegates in a faction loyal to convention president Charles I. Cassell, an architect who is a longtime D.C. Statehood Party figure. A smaller number are independent or supporters of City Council member Hilda H. Mason, also a Statehood Party figure, who as the nominal leader of the convention's second major faction had competed unsuccessfully with Cassell for the presidency.

The committee chairmen include several present and past city officeholders, including school board member Barbara Lett Simmons, head of the committee that will write the executive functions in the new constitution; City Council member Jerry A. Moore Jr., head of the preamble and rights committee, and former school board and council member James Coates, head of the finance and taxation committee.

The delegates, elected by city voters last November, have now chosen their officers, organized committees and adopted rules to govern the 90-day convention. They have allocated a $150,000 budget, selected permanent headquarters and brought in staff and office equipment. They will soon start forming witness lists and scheduling committee hearings.

Under present law, the writing of the constitution must be completed by the end of May. It must then be approved by city voters, Congress and the president before statehood can be implemented.

Beneath the usually friendly buzz of activity at convention headquarters on the ninth floor of the old Pepco building at 10th and E streets NW, factionalism continues to shape the assembly, with some delegates concerned that the same Cassell-Mason division that split the convention during its organizing phase will continue in the drafting of the constitution.

The Cassell faction is almost exclusively black. It pushed for a strong, centrally organized convention with maximum authority vested in the president and executive committee. It grew in part out of an informal "black caucus," which, according to observers including some black delegates, feared an attempt by the white minority to take over the convention. Twenty-eight of the 45 delegates are black. Seventeen are white.

The Mason faction is primarily white (both Cassell and Mason are black) and pushed for a greater sharing of power and responsibility between the officers and the committees of the convention. Its members, including a counterpart "white caucus," range from conservative Republicans to socialists, while the Cassell faction tends to be more politically centrist.

During debate over convention rules, for example, the Cassell faction pushed through a provision that the convention president can be overturned on a procedural ruling only by a two-thirds majority of the delegates, rather than a simple majority, as urged by the Mason group.

On the other hand, the Mason faction, with the help of some "crossovers" from the black caucus, got through a rule that committee chairmen be selected by the committee members rather than appointed by the convention president.

In the end, however, the Cassell faction appears to have maintained the upper hand, though some members say it is beginning to lose cohesion. James W. Baldwin, former D.C. Human Rights Office director, and Janette Hoston Harris, a University of the District of Columbia history professor, both key Cassell supporters, captured the first and second vice presidencies.

Racial tensions rarely rippled to the surface during meetings and appear to be subsiding now. But delegates, both black and white, said in interviews that many of the votes on key issues were racially motivated.

Brian P. Moore, a white delegate from Ward 2 and one of the few to complain openly, called for redoubled efforts at racial harmony.

"At first, sure, it was racial," said Baldwin. "The votes were running 100 percent white and 80 to 90 percent black on critical issues , but since then, I've seen an improvement. . . . It's more like 60-40 or even 50-50 now."

Even in such a generally liberal gathering as the statehood convention, Baldwin said, some mistrust of whites by blacks remains, "and it deals with past experiences over a long period of time." Within the black caucus, he said, "there was a definite feeling that the convention president should be black . . . and that it should be somebody involved in the statehood movement."

Also, said Ward 6 delegate Howard Croft, a UDC urban studies professor, "it was important that the treasurer be black. . . . That's a sensitive position. Some of the whites may have seen this as antiwhite feeling. But it's not. It's a matter of black pride. You know, the old stereotype about how blacks don't know how to handle money."

The final result: Six of the convention's eight officers are black. Only the third vice president and the assistant secretary are white. Three of the eight officers, including Cassell, are Statehood Party members, four are Democrats and one is a Republican.