Several other governors — Deval L. Patrick of Massachusetts; Tim Kaine, another former Virginia governor; Christine O. Gregoire of Washington; John Hickenlooper of Colorado;Jay Nixon of Missouri — may also be tempted. Even some current mayors, including Cory A. Booker of Newark, Rahm Emanuel of Chicago and R. T. Rybak of Minneapolis, may be potential future candidates.

Mr. McCain mocked Tea Party-allied Republicans in the House for believing — wrongly, he said — that President Obama and Democrats will get the blame for a default if Republicans refuse to increase the nation’s debt ceiling.

By that flawed logic, “Democrats would have no choice but to pass a balanced budget amendment and reform entitlements and the Tea Party Hobbits could return to Middle Earth,” he said, quoting a Wall Street Journal editorial.