Elements of the US right would appear to be operating on the basis of pure self-interest. For instance, we know from the little bit of research there is on the political views of the richest Americans that they are uniquely obsessed with taxes and regulations, almost to the exclusion of all else. In many ways, these people live in their own country-- one that they sometimes see as under threat from the massive one the rest of America lives in. But other elements of the US right are fanatically idealistic, even selfless, to the point where (as someone else said above) they become threats to the continued electoral success of the party of the right (the GOP) in general. These true believers, a very much non-trivial number of whom actually hold elected office at the state and national levels, seem willing to risk everything on the alter of smaller government (think of the people who seriously argued that the chips should have been allowed to fall where they may during the financial crisis in 08) or the restoration of God's Law to the center of civic and cultural life in the US. And, right now, its the latter who are the driving force on the American right. The question is: How serious are they about confronting the very powerful forces of pure economic self-interest on the right? How far are figures like Josh Hawley or Tucker Carlson actually going to go in their idealistic championing of ordinary, god-fearing Americans against the prerogatives of the global capitalists with whom they share a party?
As for the left, it depends on whether you mean "liberals" or the actual, anti-capitalist left (a still very tiny force in US politics vs. both conservatives an liberals). The actual left is characterized by an immediate and practical concern to modernize US political culture and institutions before they collapse entirely. They think perhaps some form of democratic socialism might come out of this process, but its a still very remote vision and goal for most. As politics, this is both self-interested and other-concerned. Liberals within the political class of the country, on the other hand, tend to be more affluent and self-interested (they are very frequently obsessed simply with preserving their place in the meritocracy and all this entails-- especially their lovely neighborhoods-- and ensuring that their progeny inherits it all through, e.g., placement in elite colleges). But they cover off this obvious self-interest by avowing simple "fairness" (equal chances for all in the cutthroat meritocratic struggle that they dominate) and "decency" (civility to everyone regardless of difference, another form of simple "fairness"). And there is absolutely nothing wrong with fairness and decency. In fact, they should be a default in any society. But when very materially privileged people trot them out as a form politics, and say nothing about the deeper structural unfairness of a winners-take-all form of meritocracy, its both very off-putting and a great recipe for alienating poor and working people, and perhaps driving them into the arms of right wing populism. It's in this sense that the self-interest of liberals (for many Americans "the left" writ large) is in part responsible for Trumpism. The base of the Democratic Party is made up of mainly of self-interested, affluent people supported by a mass of poorer voters who legitimately fear what the right might do to them. This arrangement is probably not sustainable, and the beneficiaries of its collapse are going to be-- have been already as it weakens-- the far right, as ordinary people either join it or become so disillusioned that they can't be bothered to fight it.
