By showing defense minister Moshe Ya’alon the door the way he did after weeks of professional disputes between them, Prime Minister Benjamin Netanyahu made a severe political mistake.Netanyahu appeared to have solved all his problems; Yisrael Beytenu had agreed to enter Netanyahu’s narrow coalition, expanding it from an unworkable 61 MKs to a comfortable 66. The prime minister would now be served by five loyal and obedient Yisrael Beytenu MKs, rather than 24 undependable Zionist Union MKs.He was all set for the return of the Knesset from its extended Passover recess on Monday and the forthcoming passage of a two-year budget that would enable Netanyahu to pass David Ben-Gurion as the longest-serving prime minister in Israel’s history.But he erred in showing Ya’alon the door the way he did.Perhaps the blow could have been softened and Ya’alon’s departure prevented had Netanyahu made clear to him immediately when they spoke on Wednesday that, at the moment Avigdor Liberman’s entrance into the government was finalized, Ya’alon would become foreign minister.Instead, Netanyahu hesitated and perhaps decided against giving Ya’alon the job.He might have even decided to continue to keep the portfolio for himself. Either way, by his own actions and inaction, Netanyahu may have created a political monster. Until now, there was no political alternative to Netanyahu who had any chance of beating him.He had overcome, for the most part, the Palestinian wave of violence that has put his career in jeopardy. Zionist Union leader Isaac Herzog had become political carrion and Netanyahu was already elected as the Likud’s candidate for prime minister in the next general election.Now, Ya’alon, who announced his intentions to seek the national leadership, can attempt to build a new bloc that can defeat Netanyahu on the Center-Right.There is no shortage of candidates to join a bloc: former Likud ministers Gideon Sa’ar and Dan Meridor, current minister Moshe Kahlon and outgoing Yisrael Beytenu MK Orly Levy-Abecassis, to name a few. He also could bring in another former IDF chief of staff, such Benny Gantz or Gabi Ashkenazi. The latter will respond to Ya’alon’s departure for the first time at The Jerusalem Post Conference in New York on Sunday.The only chance there was of Netanyahu being defeated was by a security figure whom Israelis trust. But Gantz and Ashkenazi lacked political experience and skill, while Ya’alon has both, and so will present a formidable challenge to Netanyahu.