Sen. Robert J. Dole (Kan.) had said he wouldn't do it without Vice President Bush. But now that organizers have agreed to change the date of the "Firing Line" debate of Republican presidential candidates from Sept. 2, which Dole said was too early, to Oct. 28, Dole has decided to participate. Bush has yet to change his mind about not participating.

The GOP debate is one of more than two dozen scheduled for the 1988 presidential primary season -- so far. Six debates have been planned for the South, but even so, a group of southern leaders headed by former governors Charles S. Robb of Virginia (D) and Lamar Alexander of Tennessee (R) announced last week that they are sponsoring four more debates. Robb and Alexander said the debates scheduled for Atlanta, New Orleans and Miami before the March 8 "Super Tuesday" primaries will ensure that presidential candidates pay attention to the South.

The League of Women Voters, fighting to remain the major sponsor of debates, is holding four sets of primary debates and last week announced plans for three presidential debates and one vice-presidential debate. The league has competition here as well: the Republican and Democratic parties announced in July that, in 1988, they will sponsor debates for the first time and scheduled them for Sept. 14, Sept. 25, Oct. 11 and Oct. 27.

Grant Thompson, executive director of the league, said the parties' claim of commitments from the candidates to participate may not hold. "The time to wonder about commitments is after the conventions . . . when the parties fade into relative obscurity and the campaigns take the fore."

The league debates will be in Birmingham, Boston, Los Angeles and Minneapolis in September and October 1988. Each city promised to raise $250,000 toward the costs and provide 300 volunteers.