Clinton said something to the effect of, "He comes from a privelged background, and could have avoided Vietnam, but when the call came he said send me..."
Not exactly true. He said, don't send me I'm going after my degree. He got a deferment. Then he said don't send me I'm going for my Masters. He got a deferment. Then he said don't send me I'm going for my Doctorate. He didn't get a deferment, knew he was going to be drafted, they needed officers badly, and only then enlisted.
It's being reported as a dig on Bush, but perhaps it was a dig on himself. Clinton did, after all, dodge the draft and leave the country for school and to avoid the draft.