A Democratic Republic
In Chapter Seven of TOSAIE, Popper offers his alternative to Plato's totalitarian state, which is described in his misleadingly titled Republic. Popper argues for the democratic republic, not because its decision are likely to be perfect, or perfectly reflect the "will of the people," but because it offers a convenient and nonviolent way to remove tyrants and other corrupt rulers. Those advantages should be in clear focus for Americans today.
For me, this argument is both persuasive and unassailable. Contrary to Plato's static state, it is inherently dynamic, an absolute necessity in a dynamic world. Of course the static state was a total illusion even in Plato's time, but he was blinded by his faith in his theory of forms.
Of course these ideas do not originate with Popper. They were explicitly embodied in the US Constitution and many ideas which preceded it and formed its basis.