Does a defendant have to prove that they would have taken the same adverse action even if they had engaged in protected activity?

Nevertheless, defendants may assert a defense that they would have taken the same adverse action even absent the protected activity -- the so-called Mount Healthy defense. See Nagle v. Marron, 663 F.3d 100, 111 (2d Cir. 2011) ("[P]rotected speech could not substantially cause an adverse action if the employer would have taken that action in any event . . . ."). See generally Mt. Healthy City Sch. Dist. Bd. of Educ. v. Doyle, 429 U.S. 274, 285-87 (1977). Defendants must prove a Mount Healthy defense by a preponderance of the evidence. See Smith, 776 F.3d at 119.