The odds on Washingtonians getting a chance to vote this fall on the legalization of gambling improved yesterday.

The D.C. Board of Elections and Ethics formally accepted petition forms containing 15,359 signatures and decided that, if enough of them are valid, the issue will be certified for a referendum on the Nov. 6 ballot.

The board said the signatures will be checked by a random statistical sampling method that should assure 95 percent accuracy.

Then, starting next Sunday, copies of the petition forms will be posted publicly and the validity of any signature can be challenged for 10 days by opponents of the proposed referendum.

The Rev. Andrew Fowler, a Baptist minister and executive secretary of the Committee of 100 Ministers, who was in the audience at yesterday's board meeting, said the signatures will be challenged.

"Anything we can do to prevent this great evil from being imposed on the people, we will do," Fowler told reporters.

The petition forms had been filed with the board on Wednesday by the D.C. Committee on Legalized Gambling, a citizens organization. Cecily Collier, the board's acting general counsel, said the issue qualifies for the ballot in all other legal respects.

At least 12,451 valid signatures are needed to get the issue onto the ballot. In addition, the city's new referendum law requires that the voters who signed the petition forms must represent a geographic cross-section of the city, and not just be concentrated in a few neighborhoods.

James L. Denson, who was sworn in yesterday as Mayor Marion Barry's appointee as elections board chairman, said the board had not received any complaint about the hiring of young people to solicit signatures for petitions. "Therefore, it is not an issue," he said.

Questions has been raised informally whether this hiring violated the referendum law.

Another board source that that an accusation of illegality in hiring solicitors would not invalidate the signatures, but could lead to a separate criminal prosecution.