This is actually quite an interesting problem, unique to the modern problem of representative democracy itself.
First, modern democratic societies generally hold individual subjects (and their individual "souls") morally and legally accountable. We rule out collective accountability of families, generations, races, as were common in premodern societies. This is why Trump's proposals to kill the families of terrorists or Israel's destruction of the family homes of Palestinians appear repugnant and regressive.
Second, as Trump and Netanyahu might retort, this is the case only within nations and not between nation-states in conditions of war, which then brings in all the complexities of wartime conventions, which even the United States has begun to abandon...if only unilaterally. If, for example, Americans elect a president who kills some 200,000 Muslims in acts of war, then are jihadis justified in targeting American civilians as responsible voters? Conversely, in countries without representative democracy, are citizens less responsible for violent acts of their leaders and militaries?
In the case of representative democracy, of course, voters are not entirely passive. There is an enfranchisement and "act" for which they could be held accountable. Yet they are not moral agents or "wills" continuous with those who represent them. Once power is invested in the representative, moral autonomy is dispersed. Even with powers of immediate censure or impeachment voters can only respond to moral acts already undertaken. There would seem to be a kind of limited and partial culpability. This might inevitably get "generalized" beyond individuals in states of war. Morality does not seem to fit well with modern statistical contexts.
The question of class and revolution is somewhat different. A class may be defined as functioning more or less consciously in its own interests. In republics with serfdom, slavery, extreme property or gender inequality, or other practically limited franchises, a dominant class might well be held accountable for representatives acting in their own interests "legally" but immorally against members of their own nation. Though again with some limits to culpability. In most of the modern revolutions, from France to Russia, the elimination of a dominant, "enfranchised" class was driven more by political-military expediency than moral consideration.
Apart from all these armchair considerations, there are the practical operations of modern capitalist, democratic societies, where the individual is the operative unit, the financial identity, the primary form of representation, and the legal subject. Except for oppribrium and future elections, how does one go about holding voters accountable? Presumably their bad decisions result in various forms of "blowback" or what the Greeks would call the forces of Nemesis. Unfortunately, modern news cycles, national borders, global economies, and media ideologies are such that voters rarely recognize any link between their own votes and later consequences. Where causality is so diffuse or statistical, so too is any sense of moral accountability.
Note: I am not familiar with contemporary political and legal philosophy as it applies to these issues of "representation," so I apologize for the lack of references. I hope others can provide.