It's the money that makes candidates jump in early, with palms outstretched, but nobody forces them to make such a commitment. Why?
Because of the sheer, crushing lower that comes with the office? There was always that, even in Madison's day. What's different, and worse, is that the power has in our own time become incalculably vast -- a sign of our reliance on government for the good things of life. Not just for safety and protection and security of contracts, as in the old, old days, but for Medicare and Social Security and education funding and highways and management of the environment and the encouragement or discouragement (through tax policy) of nearly every human endeavor.
You bet people want that kind of power over other people, and that, to get it, they'll move those proverbial mountains.
Our early presidential campaign reflects the accretions of government power over the decades and, correspondingly, the erosion of that space in which humans act out their personal dreams and aspirations.
The campaign is too long because government is too big, and because too many people perforce want to work its levers -- substituting their own dreams (if any) for ours. That's what we ought to notice about the campaign.
Ten to one we don't. The candidates wouldn't like it. How much sexier it is, talking of how to use all that power rather than how to dissolve it.