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. “This is the kind of crack political thinking that turned Sharron Angle and Christine O’Donnell into G.O.P. nominees,” he jeered, referring to two losing Tea Party...