WASHINGTON  A top adviser to Senator John McCain says Mr. McCain believes that President Bush’s program of wiretapping without warrants was lawful, a position that appears to bring him into closer alignment with the sweeping theories of executive authority pushed by the Bush administration legal team.

In a letter posted online by National Review this week, the adviser, Douglas Holtz-Eakin, said Mr. McCain believed that the Constitution gave Mr. Bush the power to authorize the National Security Agency to monitor Americans’ international phone calls and e-mail without warrants, despite a 1978 federal statute that required court oversight of surveillance.

Mr. McCain believes that “neither the administration nor the telecoms need apologize for actions that most people, except for the A.C.L.U. and trial lawyers, understand were constitutional and appropriate in the wake of the attacks on Sept. 11, 2001,” Mr. Holtz-Eakin wrote.

And if Mr. McCain is elected president, Mr. Holtz-Eakin added, he would do everything he could to prevent terrorist attacks, “including asking the telecoms for appropriate assistance to collect intelligence against foreign threats to the United States as authorized by Article II of the Constitution.”