This is the cookie-cutter flaw of utilizing an analogy that isn’t analogous enough. The author assumes that because politicians and scholars both try to convince others of their views, the methods that work for scholars will work well for politicians, too.

This isn’t relevant to the argument. Whether or not it’s difficult to come up with charitable positions, the author’s argument is that politicians should do so.

The politicians’ and scholars’ audiences are quite different—one is trying to appeal to voters and the other is targeting professional scholars—so it doesn’t matter if the different argumentation styles might be suited to similar audiences.

The author tells us in the argument’s context and premise that politicians and scholars attempt to persuade voters and colleagues. This is a fact the author provides as part of the foundation for the argument, not a flaw in the argument structure itself.

The author doesn’t say that politicians always paint their opponents’ positions as implausible, just that they “typically” do. We don’t know if she makes this presumption. Even if she did, it would be irrelevant to the conclusion that politicians should adopt scholars’ methods.