When Mitt Romney and Paul Ryan address the AARP on Friday, good manners will no doubt keep them from asking this question: How can that lobby claim to speak for American seniors given its partisan role in passing ObamaCare?

Thanks to just-released emails from the House Energy and Commerce Committee, we now know that AARP worked through 2009-10 as an extension of a Democratic White House, toiling daily to pass a health bill that slashes $716 billion from Medicare, strips seniors...