The Iranian strategy is to make Trump, the guy who pressed the big red war button, look stupid and to position themselves better and more aggressively, regardless of American domestic politics.
Have we actually seen anything from the Iranian leadership claiming they want a blue wave in the midterms? If not I would quibble with your use of the word “explicitly”
I think it’s a little America-centric to think they’re explicitly invested in the opposition party winning. Especially considering there are plenty of Democrats who thirst for Iranian blood. Whether the Dems win or not, the Iranians will be in a stronger negotiating position after the midterms. That’s the point of their strategy.