I got the answer right but I struggled for 5 mins to figure out how the premise supports the argument-- if it does support, it means that the opponents' political agendas are understood by large people, therefore they are not muddled and incomprehensible, then the criticism is insincere. However, how we know if their political agendas are understood by people or not? I asked ChatGPT and it says there's a hidden assumption that "Politicians would not criticize an opponent unless they believed the opponent’s agenda had some real chance of mobilizing people.". It lights me up, but I am thinking, I won't be able to build a logical system to think of this hidden assumption. For some questions (like this one which the conclusion is easy to identify and structure of argument is clear), I won't have to spend too much time digging the logics.