Politico has an
article considering the possibility that Israel might use its nuclear weapons against the hardened nuclear sites in Iran. This is thought to be possible in the event that the U.S. will not assist Israel in bombing Iran's bomb-making sites.
Use of nukes is an issue that has arisen in the GOP debates. I expect surfacing the possibility is another step in the psywar aimed at the mullahs in Iran or at a U.S. president, or both.