I don't see how -- it's a warrant application, not evidence admitted and presented to a jury, and approving a warrant is discretionary so long as the judge finds probable cause. If the judge approved the surveillance warrant it's not invalid just because one thing he considered turned out not to be true (and btw, no one has even tried to disprove what is in the infamous dossier either....I would bet most of it is probably true although it can't be proven).

Maybe if they could prove the judge abused his discretion and deliberately approved a warrant for his own political reasons when it was clear there was no probable cause .... but good luck with that one. So anyways, if you're getting into fruit of the poisonous tree doctrine, hardly a chance. That usually comes into play when there is no warrant.