Virginia Democratic Party Chairman Alan A. Diamonstein is expected to call an emergency session of party leaders this weekend to settle a bitter dispute between the party's two candidates for governor, officials said today.

Diamonstein wants the party's 202-member State Central Committee to decide whether a credentials committee was properly elected to oversee delegate challenges filed by Lt. Gov. Richard J. Davis, who apparently lost the party's nomination for governor earlier this month to state Attorney General Gerald L. Baliles.

If the party leaders, who are expected to meet here, perhaps as early as Sunday, vote to change the credentials committee, it could spell trouble for Davis' efforts to deny Baliles the nomination. Baliles has claimed enough delegates to win the nomination at the party's June 7 nominating convention.

Davis is planning to challenge as many as 750 Baliles delegates and is thought to have the support of a majority of the credential committee members. But Baliles, in a move to head off those challenges, has questioned the authority of the credentials committee, saying it was improperly elected Feb. 2 by the state central committee.

The Baliles campaign has argued that Davis is risking party unity in the fall by trying to win through a parliamentary battle what he lost in caucuses across the state. The Davis campaign has rejected pleas that the lieutenant governor concede the race.

An effort by aides to Democratic Gov. Charles S. Robb to mediate the dispute last Saturday collapsed after two inconclusive private meetings with Baliles and Davis representatives. Baliles' campaign and sources close to Robb said today Davis' campaign backed out of the meetings after initially appearing ready to compromise.

Today's development followed a contentious and embarrassing series of events for the Democrats on Saturday in which the temporary credentials committee met throughout the day and night despite an order from Diamonstein that it was improperly convened.

Meanwhile today, former Republican Attorney General J. Marshall Coleman of McLean, a candidate for the GOP nomination for lieutenant governor, released a poll that showed him far out in front of his party rivals, results two of his four opponents dismissed as self-serving.

The poll by Arthur J. Finkelstein & Associates, a national firm that generally has conservative Republican clients, contended that Coleman has more favorable ratings and name recognition than the other candidates named in the poll, conservative publisher Richard J. Viguerie of McLean and State Sen. John Chichester of Fredericksburg.

Chichester said he has a "jaundiced" view of the poll since a similar one last year showed Coleman ahead when he was considering a race for governor. "If he believed in those polls, he'd be running for governor," Chichester said.

Tim Gresham, Viguerie's campaign manager, said his "hard count" of delegates to the GOP's June 1 convention in Norfolk shows Viguerie, Coleman and Chichester about equal in delegate strength with more than 1,000 delegates still to be chosen. Gresham said his survey of delegates showed "Mr. Undecided is running a close second" to all three candidates.

State Del. A.R. (Pete) Geisen of Augusta County and Maurice Dawkins, a Washington consultant from Northern Virginia, were not included in the Coleman poll.