“Liberty requires restraints on popularly-elected leaders, as well as from minorities, so that the individual is protected from undue and arbitrary coercion by the state. These restraints are provided by a plurality of more or less equal and independent groups which check and balance one another's power.”

There is no way to restrain a politician except not re-elect them. They have made so many rules in their favor, it is difficult for any challenger to win.

Accurate enough — maybe a little awkwardly stated but overall, I like it. By example, I'm not sure liberty in and of itself "requires" but rather, the protection of what liberty describes requires vigilance in an atmosphere evil or aspiring men.