Here is a summary,

“Popper also argued that two-party systems, such as found in the United States and Great Britain, are superior to proportional representation systems; he reasoned that in a two-party system voters are more easily able to assign failure or credit to a particular political party, that is, the one in power at the time of an election. This in turn fosters self-criticism in the defeated party: “Under such a system … parties are from time to time forced to learn from their mistakes” (All Life Is Problem Solving, 97). For these reasons, government in a two-party system better mirrors the trial-and-error process found in science, leading to better public policy. In contrast, Popper argued that proportional representation systems typically produce multiple parties and coalitional governments in which no single party has control of the government. This makes it difficult for voters to assign responsibility for public policy and thus elections are less meaningful and government less responsive. (It should be noted that Popper ignored that divided government is a typical outcome in the U.S. system. It is relevantly infrequent for one party to control the presidency along with both chambers of the U.S. congress, thus making it difficult for voters to determine responsibility for public policy successes and failures.)“

I honestly just don’t think it’s a great argument.

But it doesn’t necessarily have to be proportional anyway.

I like this method,

https://en.wikipedia.org/wiki/Instant-runoff_voting?wprov=sfti1#