I don't think Motti Steinmetz will have any effect
Possibly. It depends on how things play out, and how different parties/politicians/press harp on it. So far, I think it might have had the effect of causing Smotritch to lose respect by some. He seems to be acting immaturely. I think that if played correctly, Lapid and Lieberman's responses could cause some moderate (or "sane" in Israeli parlance) people who contemplated voting for them switching their vote elsewhere.
It would be interesting if UTJ would be able to pull off a TV ad over this, not in order to bring votes to them, but rather in order to cause people to withdraw votes from radical anti-Yiddishkeit elements such as Lapid, Lieberman, and possibly others. With some good creative minds I think they could come up with a very effective message.