That's not the point he's making, its that Kerry is neglecting his duties as a Senator while he's campaigning.
Kerry has no real "duties" as senator other than to represent the will of the people of Mass. He has no duties beyond this, only abilities, like the ability to vote on bills and whatnot. I think that the people in his homestate want him campaigning 24/7 across the country, so he seems to be fulfilling his duties just fine.
If Kerry was in some other position that required constant supervision, such as presidency or governership, then perhaps it would be different. I would have to consider it in whatever context in that type of situation.
His duty as Senator is to represent the people of Massachusetts in the Senate. If he is not going to vote on legislation important to his constituents, then I would say that he is neglecting his duties and his responsibilites to the people who elected him.
