Secret Service Director Mark Sullivan told a House subcommittee that the decision is up to the candidate. He said that the Secret Service has discussed the issue with McCain's staff.

The rival Democratic candidates, Sens. Hillary Clinton and Barack Obama, already have protection. Clinton, as the wife of a former president, had agents assigned to her long before she was a candidate while Obama requested protection in February because of threats.

Major presidential candidates have been offered protection since U.S. Sen. Robert Kennedy was fatally shot in 1968, moments after claiming victory in the California primary.