Robert Carlton is an Assistant U.S. Attorney General.
He is not just a U.S. Attorney - he is an assistant Attorney General, as in the guys who run the Justice Department. As in very high up the food chain in the Cabinet branch that prosecute those that break the laws of the Republic.
He is definitely not a spy - not even close.
When, early on in the first adventure we have of his someone he was meeting worried that maybe he had been followed, he retorted without thought or knowledge, "why would someone be following me?" That is how out of his depth he is as life drops him floundering into a quagmire where government assassins wield a heck of a lot more permanent power than do the lawyers.
I would love to say that Carlton is a good guy fighting the good fight to protect the good people. Well, he pretty much is but this man has major issues when it comes to the being a good guy part. So much so that when he starts getting into trouble and the world seems to press down on him, it is hard to worry too much about his well being.
Case in point, when we are introduced to him, we learn that he wore an expensive and fancy sailing watch not because he sailed but because he "liked the image the watch presented. Like his car and clothes, the watch was a symbol of what he wanted his friends and colleagues to think about him." That sort of status seeking remains.
He is married to Tracie and father of two almost teenage boys but even there his likability is on the low end. He muses at one point that his wife "was too wrapped up in her own sense of entitlement and social ambitions to take on the uphill challenge of changing the boys' attitudes. Robert didn't notice his own lack of proactive attention to the matter."
So Carlton is not a stellar individual. He is, however, someone who gets into very nasty situations with the fate of the nation hanging in the balance and when push turns to shove, he steps up. That is important.