A close adviser to Vice President Al Gore said he had received an anonymously mailed package today that involved material designed to prepare Gov. George W. Bush for his debates with Mr. Gore.

The adviser, former Representative Tom Downey of Long Island, N.Y., said he examined the materials briefly before giving them to his lawyer, who turned them over to the Federal Bureau of Investigation this afternoon. Mr. Downey, who has been helping Mr. Gore prepare for the Bush debates and was standing in for Mr. Bush in mock debates, also said he would recuse himself from any further debate preparation.

The Bush and Gore campaigns are to meet on Thursday to negotiate the debate schedule. If the candidates adhere to a plan set up by a bipartisan commission, the first debate will be on Oct. 3 in Boston.

Campaign officials said they did not know if the materials sent to Mr. Downey had been stolen from the Bush campaign or were meant to trap the Gore adviser in some sort of dirty trick. Mr. Downey's lawyer, Marc Miller, said the material -- a videotape and a sheaf of papers -- arrived in an envelope postmarked Austin, Tex., where the Bush campaign has its headquarters.