Since then, Mr Bennett has created his own power-base in the Jewish Home Party and makes no secret of his ambition to be prime minister, “after Netanyahu”.
The last thing Mr Netanyahu wants is to give his young rival a leg-up.
He is also aware that once the former commando officer is in the defence minister’s office, overlooking IDF Headquarters in Tel Aviv, he will be challenging him constantly on defence policy, a field in which the prime minister is used to having the final word.
Mr Bennett is serious with his threat. But both he and Mr Netanyahu were thrown off-balance by the sudden move of the third contender for right-wing voters.
Sources close to Mr Netanyahu were briefing on Wednesday evening that the Prime Minister was preparing to refuse Mr Bennett’s demand.
Avigdor Lieberman’s surprise announcement that he was resigning in protest over the terms of the ceasefire with Hamas in Gaza, which he described “a surrender to terror”, has put him back in the position of the “ideological” right-winger.
It follows months during which Mr Bennett has been criticising him for being weak on Hamas.
Languishing in the polls, Mr Lieberman took the opportunity of the latest ceasefire in Gaza, mediated by Egypt on Tuesday, and anger among parts of the Israeli public that the IDF has not been ordered to strike hard, and resigned.
A central feature of the upcoming election, which either way must be held at some point in 2019, will be the three-way contest for right-wing voters between Likud, Jewish Home and Mr Lieberman’s Yisrael Beiteinu.
Mr Netanyahu is expected to form the next coalition after the election — no other party will be anywhere near Likud, if the polls are anything to go by — but the relative size of the other two right-wing parties will determine if they are invited to join, the portfolios their ministers will hold, and how much of a hold they will have on the prime minister.
Another critical consideration for Mr Netanyahu is the level of loyalty he will command in his next government.
He wants to ensure that he will still have a majority in the Knesset that will continue to support him after he is indicted by the attorney general, as now seems inevitable.
That is why he wanted to control the timing of the election and its agenda. Now, Mr Lieberman has fired the election campaign’s starter-pistol and has dictated that the handling of the Gaza conflict must be an issue on the electoral agenda.
The only way it seems that Mr Netanyahu can stop the race and try to take back some control is by giving Mr Bennett what he wants.
It all happened so quickly.
As recently as Sunday, the Prime Minister was in Paris at the Armistice centenary commemoration, explaining why he had greenlighted an agreement to allow a $15 million Qatari payment to the Gaza Strip. Mr Lieberman was grumbling but staying put.
Then, a few hours later, a covert intelligence operation in Gaza was revealed and descended into a pitched battle in which one Israeli officer and seven Hamas fighters were killed.
Next came Monday’s escalation, when Hamas fired 460 projectiles towards Israel over 24 hours and then, again, ceasefire. By now Mr Lieberman had had enough and seized his moment.
An Israeli television news poll on Wednesday evening showed that the Prime Minister was indeed damaged. Only a few months ago, Likud was polling at 35 seats; this week they were down to 29.
This is not how Mr Netanyahu saw his election strategy unfolding. He may have to swallow Mr Bennett’s promotion just to try and get back on track.
But even in a such a difficult week, he can look at the polls and comfort himself — there is no one else currently on the horizon threatening his premiership.
His right-wing-religious base still has a clear majority and the main opposition parties — Yesh Atid with seventeen seats and Labour with 11 — are not even in the running.
