This is not so black and white. In USA the universal became the norm only in XX century and it did not necessarily correspond with the strengthening of the republican system. And very few if any people in position of power in US are recruited from the lower class. I assume that most of leading positions are occupied by the rich.
BTW, in local government when the salaries are restricted to symbolic low level only rich can afford to be in the office.
Class and wealth are not synonymous. There are many people in positions of power in the US that have risen from humble means. We do not have a class system here, as it is understood in Europe. There is no such thing as "rising above one's station". Power is the reward of the successful, and as long as success is available to all who strive enough, so is political opportunity.