If Biden changes course and ends the genocide, he will not lose the Jewish people, he will only lose the Zionist people. These Zionists are a small sliver of the American electorate.
Of course a change in position would have to be accompanied by a change in propaganda. The onesided pro-Israel rhetoric spewed by him and his press team would have to change to a humanist, anti-war stance. They could start by highlighting some of the atrocities committed by Israel instead of downplaying them. MSNBC and local news would quickly follow suit and pick up the party line. People should be talking about a mass grave with 400 bodies instead of a broken window at Columbia.
Obviously there would be a loud backlash from prominent Zionists, but again in the big scheme of the electorate they matter very little. The current Biden strategy of forfeiting the young, the anti-war, and the Islamic demographics would be significantly worse.
You can call this idea farfetched, but thats only because Biden is so entrenched in his position. I believe it's the best option to save the Biden presidency and avoid a Trump second term.