You can’t really discredit your opponents; they can only discredit themselves. With that in mind, what is the best way to deal with Trump?
He won the election by promising to bring back the economy of 2019. He is entitled to try. If he fails–and I have no doubt that he will, unless he gives up his tariff and deportation scheme–the blue team needs to point it out, day after day.
Peaceful demonstrations and litigation are the proper response when Trump crashes through the guardrails and threatens liberal democracy. For more day-to-day stuff, however, the polls and the markets will be the best remedy.