Political attachments are so irrational but irrationality is not the opposite of rationality, is it?
It depends on who's doing the talking. Irrational can mean not endowed with reason, hence unreasonable, and hence illogical, absurd, and thus an opposite of rationality.
But it also can simply mean not in accordance with reason, meaning, operating in a mode that differs from reasoning. Perhaps a sensing mode, or a mode that follows intensities, that responds to as yet inchoate feelings, an affective mode. Maybe a better term for this is "nonrational," that which always accompanies the rational.