As noted below, the McCain campaign is already using a member of the military -- General Petraeus, to be precise -- as a prop in an attack on Obama, sending out a campaign email bearing Petraeus' image to raise money and slam Obama on Iraq.

The Obama camp's response? On a conference call with reporters moments ago, Obama advisers pointed to a rather relevant letter sent out just a few days ago by the Joint Chiefs urging that members of the military stay out of the presidential race.

"The U.S. military must remain apolitical at all times and in all ways," wrote the Joint Chiefs chairman, Admiral Mike Mullen. "It is and must always be a neutral instrument of the state, no matter which party holds sway."

On the call, Obama spokesperson Josh Earnest argued that McCain had used Petraeus' image politically even though the ink was barely dry on the Joint Chiefs' directive. "It's interesting that just days later, the McCain campaign jumped in with both feet," Earnest pointed out, adding that the McCain camp had both politicized Iraq and used Petraeus to raise money.

Petraeus himself, presumably, wouldn't want his image used in such a context, given the Joint Chiefs' preference. Indeed, as it happens, Petraeus' own spokesperson has already weighed in on this topic. Last September, when Rudy Giuliani used Petraeus' image in a political ad, Petraeus spokesperson distanced the General from it, saying he had "not condoned the use of his photo" in the spot.

Late Update: Here's the audio from the Obama campaign's conference call:

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