More substantively, her attempt to position herself at all times as the anti-establishment outsider has made her seem on occasion less principled than opportunistic. She quickly distanced herself from Paul Ryan’s Medicare reform when it came under liberal fire, even as she purports to be the scourge of uncontrolled spending. Her recent opposition to the debt-ceiling deal on grounds that GOP leaders should have insisted on first passing a balanced budget amendment, while holding only the House, was a political fantasy.

Americans are already living with the consequences of electing a President who sounded good but had achieved little as a legislator and had no executive experience. Mrs. Bachmann will have to persuade voters she isn’t the conservative version of Mr. Obama.