It might, if nothing else it would probably be enough to have the US give Ukraine some of their own tactical nukes to launch back at Russia. The only reason we haven't been giving them weapons that powerful and/or with that kind of range is out of concern it might encourage Putin to go full on nuclear. So if Russsia starts doing it first, that would remove the reason to not give Ukraine that kind of firepower.so putin using a nuke in ukraine will trigger MAD.... ??