There is a lively debate among theorists of civil-military relations about the appropriate levels of political activity in which the military may engage. Some advocate fairly tight restrictions, even encouraging soldiers to emulate Gen. George C. Marshall who famously refused to vote so as to demonstrate his apolitical professionalism. Others allow for greater leeway, and encourage the military to speak out more regularly in policy debates, even when those debates have a partisan overlay.

I tend towards the restrictive end of the spectrum. I do not discourage the military from voting, for instance, but I do think it is a mistake for prominent retired senior generals and admirals to campaign actively for political candidates (I do not see a problem with veterans of whatever rank running as candidates in their own right. When they do that, they clearly cross over to the pure political side. The problem is trying to maintain the authority, even deference, that comes with professional distance while simultaneously politicking for a candidate).  

For a good introduction into the complexities of this debate, I recommend reading Risa Brooks survey of the topic: her chapter on "Militaries and Political Activity in Democracies,"  an excellent chapter in a recent compendium. (Full disclosure: I have a chapter in that same book, which I co-authored with a brilliant graduate student. I got permission to present and publish that article while still on the NSC staff because, when my superiors reviewed it, they declared it so academic and abstruse that no one would read it, and thus it would neither constitute a conflict of interest nor expose the White House to any risk of embarrassment -- or words to that effect. Sometimes, there is utility in academic irrelevancy.)  

It is also clear that there is a spectrum of opinion within the ranks. A first-rate Georgetown U. dissertation by Heidi Urben (more full disclosure: I was on her dissertation committee) documents that Army personnel have some difficulty in determining where to draw the line -- is it acceptable to encourage fellow military comrades to vote? How to vote? To demonstrate the same with bumper stickers in the barracks?

So I accept that there are gray zones in the area of military and politics and that it is especially difficult to draw clear lines for reservists who have feet planted firmly in both civilian and military worlds.

However, I am hard-pressed to think of a specialists who would tolerate this: an Army reservist, Corp. Jesse Thorsen, speaking to a campaign rally before the Iowa caucus while in uniform. Perhaps there are lawyers who will try to argue that because the corporal was not on active duty at the time he may avoid the harshest punishment. And most people will point out that a corporal is very close to the bottom of the totem pole so hardly on his own capable of destroying our democratic institutions. But this seems a pretty clear violation of both the letter and the spirit of the Department of Defense regulations.

Of equal importance, it is corrosive of healthy civil-military relations. The corporal may believe he is speaking only for himself, but the reality is that if he is wearing his uniform, his audience seems him as speaking on behalf of the institution. For that matter, almost no one is interested in what civilian Jesse Thorsen has to say; the primary reason he was invited to speak was that the campaign knew that folks would be interested in what a corporal had to say. It was his military status, in other words, that gave his political views cachet. That makes it a matter for civil-military relations and a matter for public rebuke.