A few things.

1) The linked to article brings some examples of thinking distorted by politics but does not explain the relationship between belief and political convenience. If anything, he implies there is little relationship.

In the first example, Perry already truly believes what would be convenient, and is castigated for believing the unlikely and not changing his mind, but the original reasons for his beliefs and his reasons for not changing them aren't really explored.

In the second example, in the author's opinion, Romney has not had his beliefs corrupted by what would be convenient to believe, but is merely hiding his inconvenient beliefs with ambiguous statements.

2) That guy writing about politics corrupting clear thought has clearly had his own mind badly damaged by politics (or is writing as if he had as part of his job). It is impossible to tell how much the linked to piece was motivated by its contents' truth and how much was motivated by the attractiveness of making accusations against political enemies, true or not.

I, For one, liked the article. The author might benefit from reading Politics is the MindKiller, and so on, but he has valid points, and linking to it does not, in my opinion warrant a downvote.