Claiborne B. (Buck) Morton, a McLean businessman and Republican candidate for the Virginia Senate, died Thursday of cancer in Fairfax Hospital.

Morton, 53, announced in July that he had been diagnosed as having lung cancer and tumors in the brain. He said then he would wait for the results of further tests before deciding whether to continue his campaign this fall against Sen. Clive DuVal II, the incumbent Democrat in the 32nd District, which includes McLean, Great Falls, Vienna, Falls Church and part of Arlington.

Morton, owner of two stationery stores in Fairfax County, was making his second bid for public office in Northern Virginia. He ran in 1981 for state delegate and was defeated in a six-way race for three seats.

Benton K. Partin, chairman of the Fairfax County Republican Party, said yesterday a decision on whether to replace Morton on the ballot will be announced next week, but some Republicans said it was unlikely that another candidate would come forward to run with less than two months remaining until election day.

"I don't know of any candidate available at the moment. I don't see anyone waiting in the wings," said House Minority Leader Vincent F. Callahan (R-Fairfax). "You just can't come in and raise the money and put together the organization you would need."

"We had counted on [Morton] to put up a very strong race," said Callahan. "It is quite a loss to all of us. He was a very tough guy and he had a lot of faith."

Pixie Bell, who chairs DuVal's reelection campaign, said he has done only limited campaigning since Morton disclosed his illness and suspended all election efforts upon learning of his opponent's death.

Morton grew up in Northern Virginia. He is survived by his wife, Anne, and son, Chip.