It was a strange collaboration, given the Joint List’s aversion to Israel’s military campaigns in the region and occupation of the West Bank. Mr. Gantz was the chief of staff who oversaw the devastating, 50-day war against militant groups in Gaza five years ago.

Then the numbers began to change.

Three of the 13 Arab lawmakers, from the hard-line Balad party, opposed the Gantz endorsement and demanded that their seats be withdrawn. Writing in Haaretz on Thursday, Dr. Mtanes Shehadeh, a Balad lawmaker, cited Mr. Gantz’s military record and what he called his “glorification of the murder of civilians in the Gaza Strip in the previous election campaign.”

Mr. Gantz had ignored the demands of the Arab parties, including repealing a law that declared Israel the nation-state only of the Jewish people, and denied holding talks with them, Mr. Shehadeh wrote.

The Joint List wanted to oust Mr. Netanyahu, Mr. Shehadeh wrote, “but we never promised to do so by supporting the ostensibly less dangerous candidate, Gantz, at any price.”

That brought Mr. Gantz’s endorsements down to 54, one fewer than Mr. Netanyahu.

But that may have been part of Mr. Gantz’s plan.

Ayman Odeh, the leader of the Arab alliance, said Wednesday that a Blue and White lawmaker approached him and told him that 10 recommendations were preferable to 13, because Mr. Gantz did not want to come out on top and go first in trying to form a coalition.

Mr. Gantz believed that if Mr. Netanyahu went first he would fail, Mr. Odeh explained in a Facebook Live video. By going second, he said, Mr. Gantz hoped that other parties would have to compromise and enter a Gantz-led coalition because they would be under pressure from the public to avoid a third election.