With Newtmentum still chugging along, Mitt Romney has unveiled a secret weapon to halt his sluggish polling: an endorsement from former vice president Dan Quayle? It's not really a Chris Christie or Tim Pawlenty-like get for Romney (or a Donald Trump endorsement either), but tomorrow the Associated Press reports that the former George Bush 41 veep will endorse Mitt at a event in Arizona, a "GOP official familiar with Quayle's thinking says the former vice president is backing Romney because he views Romney as the most credible candidate in the race." The immediate reaction from a sample of Beltway Twitter-types was just reflexive jokes. But maybe that's not the purpose of the endorsement: Quayle has a home in Arizona, the AP informs, and his son, Ben Quayle also represents the state in Congress.