Who is Tony Carbo from In the Lake of the Woods and what is their importance?

Tony Carbo is John Wade's campaign manager. He is described as somewhat overweight, and he refers to himself as a "pig." After John's concession speech, Tony says that he could have left the campaign a month earlier, as it was obvious John would lose. He says that he stayed, however, because he was lovesick over Kathy. Tony adds that John wouldn't have lost the election if he's only confided in him about the situation in Vietnam.