''This town has become very corrupt, there's no doubt about it,'' McCain said Sunday on NBC's ''Meet the Press'' program.

McCain, chairman of the Senate Indian Affairs Committee, has led a congressional probe of Abramoff's dealings with Indian tribes who hired him as a lobbyist. The Justice Department is investigating Abramoff's contacts with lawmakers and congressional staff members.

''There's strong evidence that there was significant wrongdoing,'' McCain said when asked whether he believed some lawmakers have committed crimes. He declined to be specific.

Michael Scanlon, a former Abramoff associate who previously was an aide to Republican Representative Tom DeLay, pleaded guilty last month to conspiring to corrupt public officials and defraud Indian-tribe clients. The plea clears the way for his cooperation with the investigation.

Abramoff, Scanlon and their lobbying clients combined to give campaign money to a third of the members of Congress.

McCain said the lobbying system needs to be restructured to eliminate fraud and to prevent groups from hiring well-connected people to make deals to pass certain legislation or guarantee funding for key issues. He said he wouldn't count on the congressional ethics committee that monitors lawmakers' compliance with laws and ethics rules.