Click here to watch "Troops."

John McCain isn't letting up on Barack Obama. His new ad, released Saturday, blasts his Democratic rival for not visiting wounded U.S. troops while overseas last week. The ad received a great deal of buzz over the weekend on various talk shows, and both camps rushed in to explain or elaborate.

"He made time to go to the gym, but canceled a visit with wounded troops," an announcer says in "Troops" (subscription). The 30-second ad refers to Obama's decision to cancel a visit to a U.S. military hospital in Germany and cites reports that the senator made time to exercise at a hotel gym earlier that day, before his speech in Berlin. The campaign said it was because the Pentagon told him his campaign staff couldn't go with him and that the visit might be viewed as politically motivated. "Seems the Pentagon wouldn't allow him to bring cameras," the announcer says, making a not-so-subtle jab at the amount of press coverage Obama has been getting; the ad concludes, "John McCain is always there for our troops." While Obama didn’t visit, he did make phone calls to wounded troops at the hospital.

Response to McCain's ad was quick. Sens. Chuck Hagel, R-Neb., and Jack Reed, D-R.I., who accompanied Obama on his trip to the Middle East, appeared on CBS' "Face The Nation" on Sunday. Hagel said McCain is "treading on some very thin ground here when he impugns motives and when we start to get into 'You're less patriotic than me, I'm more patriotic.'" Reed defended Obama's dedication to U.S. troops, citing numerous trips the three senators made in the Middle East to visit them. "That is a completely distorted and, I think, inappropriate advertisement," Reed said.

Brian Rogers, spokesman for the McCain campaign, sees both the ad's message and Obama's schedule of events overseas differently. "This isn’t about patriotism. It’s about Senator Obama's priorities," Rogers said. "The reality is he found time to go to the gym, to drink martinis with reporters in Berlin, but canceled a visit to wounded troops." Responding to the question of whether Obama may have decided against the visit because the press wasn't allowed, Rogers said, "That’s a question worth asking."

Appearing on CBS' "This Week" on Sunday, McCain also questioned his opponent's justification for canceling the visit. "I know of no Pentagon regulation that would have prevented him from going there -- without the media and the press and all of the associated people. Nothing that I know of would have kept him from visiting those wounded troops," he told George Stephanopoulos.

The ad is running in the "battleground" regions of Colorado and Washington D.C., Rogers said, and the voters in these regions are the primary target. With no concrete policy issue at stake in the spot, it has focused on Obama's character and personality. As various media outlets, such as the Politico, have reported, the McCain campaign appears to be shifting into increasingly personal territory and away from policy grounds, a line the campaign straddled with its last two ads.