I am not entirely in line with the below judgement that
... presidential contests have almost never been about a rational comparisons of policies, but instead have been morality tales framed by the respective campaigns ...
I do think that "rational comparisons of policies" are taking place and do play a significant role - especially among specialist political activists (see below).
However, on balance, infatuation with a partisan narrative is likely to be the supreme driver. But that should not surprise us, nor should it be taken as an unmitigated disaster. Here are a number of reasons why:
First, you cannot do politics successfully without a scaffolding of firm story lines. No one is going to win an election by telling their audiences how divided in their honest minds they are on most of the key issues. You need simple, consistent, firmly-held-on-to narratives to come across convincingly.
Second, only very few of us have the time to become thoroughly knowledgeable about political issues. Once you have acquired a taste for a political narrative - mostly during your youth - you are likely to cling to it. For instead of being isolated highlights, political convictions are highly interconnected networks of beliefs. If you start cutting one of them you will soon find that almost all the rest of them must go too. If it was lucrative to become a political expert far more people would have a go at it. As it is, for most people it is rational to subscribe to the spoon-fed (superficially propagandistic) convictions of their chosen political narrative and to support it with their emotions and their vote.
Third, elections/political contests are substitutes for physical brawls, even wars. This is a good thing, which, of course, involves costs. In a free society, political confrontations are part of what I call the transrational arsenal of institutions with whose help we manage to live rather well in the face of fundamental disagreements among the populace.
Fourth, for a political order to be effective, it needs to be organised - like everything else in modern society - along the lines of a division labour. So there are political specialists - such as politicians, their assistants, campaign workers, reporters etc. - which make up only a small part of the population, most of whose members play the role of non-specialist consumers of political propaganda. This need not be a bad system. And there cannot be a good system that does not work roughly along these lines. So let us not ask for too much and be content as long as the activists - many of whom serve as representatives of the non-specialists - do their job satisfactorily, and their interaction with the consumers of politics works reasonably well - i.e. does not result in an uncoupling of a small part of society from the rest of its members and an attendant usurpation of incontestable power.
Say what you may, it strikes me as a healthy sign that the American political system remains prone to be shaken up thoroughly every once in a while by outsiders like Bernie Sanders and Donald Trump.
The first two U.S. elections were essentially not contested, with George Washington as the universal preference. So the third election, which occurred in 1796, was the first truly contested election, and it immediately showed the vitriol and ad hominem attacks we have come to expect in presidential politics. In it, Thomas Jefferson was accused of lacking manliness and proper Christian values, among other deficiencies. In fact, presidential contests have almost never been about a rational comparisons of policies, but instead have been morality tales framed by the respective campaigns:
[When] we think a bit more broadly about the cultural structures of American presidential politics, then this first contested election was absolutely seminal. It set the geographic pattern of New England competing with the South at the two extremes of American politics with the geographically intermediate states deciding between them. It established the basic ideological dynamic of a democratic, rights-spreading American 'left' arrayed against a conservative, social order-protecting 'right,' each with its own competing model of leadership. One can even detect the creation of what linguist and political commentator George Lakoff calls the essential 'conceptual metaphors' of American political life, government as 'strict father' or 'nurturant parent,' but it is not necessary to go that far. Historian Alan Taylor has described a similar idea as the competing political 'personas' of Federalists and Democratic-Republicans: 'fathers' versus 'friends' of the people. It was the Federalists, especially, who got the battle of metaphors started with their efforts to emasculate the image of Thomas Jefferson, but the opposition redressed the balance with a vengeance in the attacks they mounted on the allegedly monarchical, tyrannical tendencies of George Washington and 'Daddy Vice,' as Vice President John Adams referred to himself.
Even with their patchiness, the two campaigns of 1796 managed to construct remarkably coherent images of the two candidates that connected clearly to the policy issues and cultural tensions of the day, especially those raised by the French Revolution. The young United States found its government severely pressured to choose sides in the world war that spun out of that revolution, and its politics were roiled by the democratic enthusiasms it spawned. Keynoted by congressman and pamphleteer William Laughton Smith of South Carolina, with some inspiration from Edmund Burke and guidance from Alexander Hamilton, the Federalist attacks of 1796 wrapped their caricature of Jefferson in a powerful conservative critique of French revolutionary radicalism, the Enlightenment, and post-Christian morals. With the Sally Hemings revelations still in the future, the critics focused chiefly on Jefferson's lack of manly qualities, as evidenced especially by his interest in science and technology. According to the Federalists, here quoted in a sort of dual biography of the two candidates published in Boston, the 'timid and wavering' Jefferson was not cut out to be a 'statesman, still less ... a patriot.' Woe betide America if 'her liberties depended upon the depth of his political knowledge, the strength of his virtue, or the vigour of his mind.' Jefferson's inability to 'act the man' would invite foreign aggression and lead to national ruin: 'our national honour forfeited; war probably ensue, our commerce be destroyed, our towns pillaged.' Better to opt for the 'security' of the 'resplendent abilities,' 'faithful services,' 'inflexible patriotism,' and 'undeviating firmness' of John Adams, who would have the wisdom and strength to stand against 'mad democracy' and 'the wiles of ambition.' The basic images of liberalism and conservatism in American politics have never strayed very far from this original Federalist template.
The politics of the 1790s was not a primitive (or sophisticated) competition of personality cults, or at least not any more primitive than our own. In fact, the 'informed voter' model of party politics touted in civics lessons and journalism schools, where the media provide information that allows voters to select the candidate who best matches their own policy preferences from a list of issues, has rarely been more than an aspiration in American politics. By taking a small leaf from the work of George Lakoff and other scholars of modem political culture, we can proceed on the premise that even with fully developed party politics, partisanship not only can but may most effectively be expressed in terms of metaphors and morality tales rather than platforms and arguments.
On American partisan history see also my Immigration and Freedom (8/10) - I. Feasible Freedom and Early US Immigration Politics (1776 - 1900), as well as part II and part III.