> The American and French revolutions originated in the middle classes.

I don't know about the american revolution, but that's wrong for the french revolution. I'll link to french wikipédia pages since they are far better on the subject. https://fr.wikipedia.org/wiki/%C3%89tats_g%C3%A9n%C3%A9raux_... Here we can see the first National Assembly was half nobility and clergy. The third estate was the other half.

https://fr.wikipedia.org/wiki/Tiers_%C3%A9tat > Par ailleurs, les députés du tiers état aux états généraux représentaient essentiellement la bourgeoisie[2].

Which indicate that the majority of the third estate representative were bourgeois.