Prime Minister Benjamin Netanyahu should not be allowed to become defense minister. There have to be limits to what a prime minister is able to do.Netanyahu currently serves as prime minister, foreign minister and health minister. Taking upon himself the defense portfolio – as some sources in the Likud Party suggested Wednesday – would be irresponsible, especially considering that other members of the coalition are qualified to take over from outgoing Defense Minister Avigdor Liberman.If Netanyahu were to become defense minister in addition to being foreign minister and health minister, he would be the first prime minister in Israeli history to do so. While some leaders have been prime minister and defense minister at the same time, none has ever been all four.Israel, though, needs a full-time defense minister, in light of the challenges the country faces in the region and along its borders.One option is to give the portfolio to Bayit Yehudi chairman Naftali Bennett, who has served in the Security Cabinet for the last five years and has a particular expertise in defense-related issues. Already, there are voices within Bennett’s party saying that Bayit Yehudi would leave the coalition and topple the government if the defense portfolio is not given to him.Bennett is not the only option. Netanyahu could bring in someone from outside the government or give it to another member of his party. Bennett’s leverage is that he could pull his party out of the government and topple it, if he doesn’t get the prestigious portfolio.The question Netanyahu needs to ask himself is whether Liberman’s resignation is worth going to an election over. While his relationship with Bennett is known to not be the best, why should the country go to an early election as a result?Government stability, especially in light of what just happened in Gaza, should always take preference over an early election.