It seems that the "farmer" in your question is symbolic, if not, my apologies. It isn't clear whether you are referring to GB or THE GB, but the distinction may be immaterial. What you are asking, IMHO, is not a question of the way things work as much as it is a question of human nature. Probably, at its core, the issue is the same as wondering why ponography is the leading industry on the internet, why the greatest concern among western youth is whether their telephones can take pictures, and why, after removing the commercials, the "opinions", the fluff and gossip, that out of a 24 hour day, CNN has approximately 37.5 minutes of actual news. It is what some have called the "fantasy" factor.
Lenny Bruce did a bit where he advised men to never to admit they ever did anything wrong to their woman. "Even if she catches you in bed with another woman, tell her, 'I don't know who this woman is. She just burst into the room, naked, saying that she was freezing to death, so I jumped on her to save her life!'" He went on to explain that your woman would believe you. Why? "Because she WANTS to believe you." (Of course, a week later the man will find himself dodging dishes, silverware, and other handy kitchen implements while his same wife screams at him because he didn't take the garbage out when she asked him to. And, being gender inhibited, he never connects the dots, so he sits in the neighborhood pub and grouses to his mates about how crazy women are.) But then, these same men will sit comfortably on the sofa wearing beer stains on their three day old tshirt while they balance the bag of potato chips on the ridge of their swollen, Homer Simpson like gut, while ignoring everything but the football on the telly, and warmly believe their wives who tell them, "Of course I love you!"
The farmer doesn't have to present a plan because, well, he doesn't have to. We don't want plans, we don't want reality, we want to FEEL good. There was a most admirable vice presidential candidate (stalwart, war hero, forthright, honest, level headed, etc.) who had been judged as a detriment to his running mate because commtting the one unforgiveable sin in America: he was bad on TV. As far as American Presidents are concerned, the question you ask has always been asked: is the job of the President to lead? That is, was he elected to see a vision for America and follow it, to set the wheels of government in motion to get from here to there? Or is he elected to obey "the voice of the people", that is, to follow? It probably depends on his poll numbers.
As regards the farmer in the guise of THE GB, you have the historic question of "kingship". Presidents are (by theory) elected by the people, therefore everyone shares blame when he screws up. Kings, on the other hand, are chosen by God, and therefore, we get what we get and we live with it. In this case, the farmer doesn't have to come up with a plan because he isn't answerable to anyone BUT God. Now, in the case of THE GB, it seems that there is a president who is appointed by God by being elected by men; however, I may not be totally accurate in my description, since I've never been privvy to such an occurance. The downside of the kingship aspect, however, is something to which God never seems to catch on (maybe He's a slow learner, but not slow as some consider slowness) namely, the "power corrupts" theory and the fact that ultimately, if God appoints a jerkoff, then God gets the blame.
So, all this being said, you will find that the farmer's "success" and, therefore the length of his tenure, will not be dependent upon his authority or how much he uses/abuses that authority to right wrongs or propel us forward in out manifest destinies, but he will be most successful who convinces the most of the rest of us that the stench is really a most pleasant aroma.