Some insight into why Jones may be moving up Obama's short list, care of Bob Woodward's State of Denial:

Shelton has been [Joint Chiefs] chairman since 1997. His four-year term would be up in the fall. Rumsfeld assigned the sensitive task of helping find a successor to Staser Holcomb, the kitchen cabinet consultant and retired vice admirial...

Holcomb had been asking to see Marine Commandant General James L. Jones, a tough, 6-foot-5 Marine who had a cosmopolitan side. Jones, who had grown up in Paris and was fluent in French, had graduated from Georgetown University in 1966 with a degree in international relations. He had joined the Marines through officer candidate school the next year and served as a platoon leader in combat in Vietnam. He'd had all the right assignments--chief aide to the Marine commandant, Marine division commander and then, in 1997, military aide to Secretary of Defense William Cohen. Cohen and Jones were close friends, going back nearly two decades when Cohen was a U.S. senator from Maine and Jones, then a major, had been the Marine liaison in the Senate. Cohen had seen that Jones was appointed commandant, the senior Marine and member of the Joint Chiefs. Jones knew that the Cohen connection made him suspect in the Rumsfeld Pentagon. ...

Still, Jones was on Holcomb's list as a possible chairman. He was called with no advance warning on a Saturday morning for an interview with Rumsfeld about the JCS chairmanship. During Rumsfeld's first months back at the Pentagon, Jones had found himself largely in the dark about what the secretary was doing. As the top Marine ... he also couldn't get copies of some of the studies Rumsfeld assigned to his civilian staff and consultants.

Jones always had time and showed respect for anyone, whatever their rank or station in life, and he was surprised by Rumsfeld's curt manner. The secretary at times didn't even say hello. Jones felt that Rumsfeld was mostly concerned with his own ideas. He gave the appearance of being deliberate and thoughtful but he often shot from the hip. Rumsfeld's self-importance and arrogance inflected everything, Jones concluded. Who would want to be his chairman and senior military adviser, given that it appeared Rumsfeld didn't really want military advice? He wanted voluminous information and detail from others, but then he would only follow his own advice.

Jones took the unusual step of declining the interview, saying he wanted to remain Marine commandant.

[New passage]

Around this time, General Jim Jones, [now] the NATO commander, paid a call on his old friend General Pete Pace, the vice chairman of the Joint Chiefs. It was virtually certain that Pace was going to move up to replace Myers as chairman.  ... Jones expressed chagrin that Pace would even want to be chairman. "You're going to face a debacle and be part of the debacle in Iraq," he said. U.S. prestige was at a 50- or 75-year low in the world. He said he was so worried about Iraq and the way Rumsfeld ran things that he wondered if he himself should not resign in protest. "How do you have the stomach for eight years in the Pentagon?" he finally asked.

Pace said that someone had to be chairman. Who else would do it?

Jones did not have an answer. "Military advice is being influenced on a political level," he said. The JCS had improperly "surrendered" to Rumsfeld. "You should not be the parrot on the secretary's shoulder."

His concern was complete. When Senators John Warner and Carl Levin, the chairman of and ranking Democrat on the Senate Armed Services Committee, visited him at his headquarters in Belgium, Jones told them about all the problems. He said they needed new legislation ... to reempower the service chiefs or make some kind of sense of the crazy system.

"The Joint Chiefs have been systematically emasculated by Rumsfeld," Jones said.

[New passage]

That week Rumsfeld was holding three days of closed-door Pentagon meetings with the combatant commanders and top civilians in Defense. Before Rumsfeld, these regular meeings had been run by the chairmen of the Joint Chiefs. Rumsfeld now ran the meetings.

General Jones, the NATO commander, told Pace he believed that Rumsfeld so controlled everything, even at the earliest stages, that they were not generating independent military advice as they had a legal obligation to do. Rumsfeld was driving and affecting the debates and decisions "politically." They, the uniformed military, should be worried about the "political spin," he said. He proposed that Pace meet alone with the combatant commanders and service chiefs--without Rumsfeld, without any Defense Department civilians. "I've got issues," he said, that needed to be addressed and debated without Rumsfeld present.

Pace agreed to hold a one-hour meeting one morning that week with just the service chiefs and combatant commanders.

At the meeting, Jones said he wanted to focus on one issue--the value of forward basing. ... Rumsfeld's idea was to bring as many of the forces as he could back to the United States. Jones argued that this was altering the basic concept and premise of American global presence. They had an obligation to state their views and fight this new theology because it would weaken the position of the United States in the world. A number of those present agreed in principle, but no one seemed willing to  take on the secretary of defense.

As a rule, I'm skeptical of putting someone on the ticket who's never run for office, and I feel the same way here. But it sure doesn't hurt Obama to float Jones as a trial balloon. The mere suggestion that he's considering Jones sends a certain message (leading to blog posts like this one)...

P.S. You obviously have to take this portrayal with a grain of salt, since Jones appears to be a major source for this material. Still, I assume Woodward double-checked it with someone.

Update: Jonathan Martin says no way on Jones, validating the message-sending interpretation:

[Jones] and McCain are close friends and have been for decades.

The two served together on Capitol Hill as military liaisions, McCain for the Navy and Jones the Marines.

Jones is an outside adviser to McCain on national security issues and the GOP nominee has made clear that he'd like to appoint his friend to a top post in his administration.

--Noam Scheiber