Ad Questions Bush's National Guard Service

Sen. John Kerry has faced a lot of questions for several weeks about the medals he won in the Vietnam War. For opponents of President Bush, it's payback time. A new ad puts Bush's service in the National Guard back under the microscope.

The ad features retired National Guardsman Lt. Col. Robert Mintz saying, "I heard George Bush get up and say, 'I served in the 187th Air National Guard in Montgomery, Alabama.' I said, 'Really? That was my unit. And I don't remember seeing you there.' ... It would be impossible to be unseen in a unit of that size." The ad is being run in swing states by an anti-Bush group called Texans for Truth.

Democrats charge that Bush failed to fulfill his duty to the Air National Guard in 1972 when he transferred from Texas to a unit in Alabama while he worked on a political campaign.

Earlier this year, the White House claimed all of Bush's military records had been released.

But now the Pentagon, responding to a Freedom of Information Act request by The Associated Press, has released more documents.

According to The AP, the newly released documents show no record of Bush performing his duty in Alabama between April and October of 1972. And they show that he missed a crucial "24-hour active alert mission to safeguard against surprise attack" in the southern United States.

White House Communications Director Dan Bartlett insists the president fulfilled his duty.

"I'm not surprised that during a campaign, and particularly at a time that President Bush has gone ahead in the polls, that all of sudden the Democrats are coming out of the woodwork to recycle old charges, old claims that President Bush didn't meet his obligation. The bottom line is that President Bush met his obligation," Bartlett said.

But the questions keep coming. Today The Boston Globe reported that when Bush applied to be discharged from the Texas Air National Guard in July 1973 because he was moving to Massachusetts to attend Harvard Business School, he signed a form that included this pledge: "It is my responsibility to locate and be assigned to another reserve forces unit."

The young Lt. Bush never joined a Massachusetts unit.

However, an official with the Air Force Personnel Center told ABC News that Bush was not required to join a unit in Massachusetts, because he was registered with a unit in Denver.

"If the Air Force wanted him for duty," the official said, "they knew where he was."

And in a conference call with reporters today, Mintz, the president's accuser in the new ad, admits he may simply not have seen Bush on base. "Is it possible he was there? I didn't see him, but, yes, it is possible."

Also today, a member of that same Alabama unit told ABC News he did see Bush on the base "five or six times."

Former Alabama Air National Guardsman James "Bill" Calhoun said, "I have no doubt in my mind that it was George W. Bush, that he made his drills. He was very professional. He came in uniform. He signed in. He was very low-key."

ABC News' Terry Moran filed this report for World News Tonight.