From the NY Times article
The purpose of the general ban, according to Major Mike Backus, a spokesman of the Maine Army National Guard, is that candidates are “not supposed to use their uniform for gain in a political venue.”
I think that he flunks that test.

From the Kennebec Journal article...
To be sure, the military assignment put a big crimp in his political ambitions. On the other hand, who among his political rivals, present or potential, is going to attack him for failing to show up to debate the issues in person? Anyone who even edges close to such criticism will only remind voters about what he's doing instead... But it makes no sense to count him out of the 2008 Republican primary just because he's not around to actively campaign. Perhaps especially so. (emphasis mine)
This is why I noted earlier that it can only be judged with certainty by the candidates themselves whether the "service was not a premeditated act to bolster their campaigns." You cannot "prove" it, but it sure looks fishy. I guess that is why I was taught, from my first year of ROTC until my last year in the Army, that we must not commit unethical acts and avoid the appearance of unethical acts. I used to think the second half of that was a bit unreasonable, but now I see why it made sense.