The No. 1 topic of conversation in Hollywood yesterday did not seem to be George W. Bush’s declaring victory in Florida on Sunday, but what will become of “Ally McBeal” costar Robert Downey Jr. The actor, 35, who had just successfully resurrected his career after serving a year in prison on a drug-related charge, was arrested Saturday night at the Merv Griffin Resort Hotel in Palm Springs, Calif., with cocaine and methamphetamine in his possession, say police. He is currently free on $15,000 bail and scheduled for arraignment on Dec. 27. “It’s so sad,” hotel owner and TV mogul Griffin told Variety senior columnist Army Archerd. Downey’s publicist yesterday told the Associated Press that plans for the actor to continue work on “Ally McBeal” remain unchanged. (“Ally” producer David E. Kelley, meanwhile, offered no comment.) Furthermore, said the rep, Downey is still committed to a Los Angeles stage production of “Hamlet” to be directed by Mel Gibson in January. Los Angeles County Deputy District Attorney Marty Herskovitz, a key figure in Downey’s previous drug case, expressed surprise over this weekend’s arrest, given reports that the actor was living clean. He also indicated to AP that Downey could face a maximum of six years and eight months behind bars should he be convicted of the potential charges stemming from Saturday’s bust.