Israel's governing coalition is falling apart, setting the stage for the fourth election in two years.

Driving the news: Defense Minister Benny Gantz announced tonight that his Blue and White party would vote in favor of dissolving parliament on Wednesday because Prime Minister Benjamin Netanyahu — Gantz's political rival turned coalition partner — was refusing to pass a budget and reneging on their power-sharing deal.

Why it matters: Wednesday's vote is only a preliminary step, but it will set an almost irreversible course toward early elections next March.

State of play: The government needs to pass its 2020 budget by Dec. 23 to survive, but Gantz is insisting that Netanyahu also agree to pass the 2021 budget by then.

• That would make it legally impossible for Netanyahu to back out of the coalition agreement under which Gantz is to rotate in as prime minister on Nov. 17, 2021.
• Between the lines: When that agreement was announced last April, many analysts doubted that Netanyahu would ever willingly give up the prime minister's post.

What they're saying: Gantz said he joined the power-sharing government due to the COVID-19 crisis and had no illusions about Netanyahu, whom he called “a serial promise-breaker."

• He accused Netanyahu of worrying only about his political survival and about saving himself from the corruption trial that is set to resume in two months.
• Gantz added that if the elections take place, he will try to form a broad government that does not include Netanyahu.
• Netanyahu released a video several minutes before Gantz’s press conference. He stressed a desire for unity and urged Gantz not to vote in favor of dissolving the Knesset.

What’s next: Gantz did leave a small opening by saying the early elections can still be prevented if Netanyahu brings the 2021 budget up for a vote in the Cabinet in the next three weeks and guarantees it will pass the Knesset soon thereafter.

• Netanyahu is unlikely to take those steps, as he has no desire to follow through on the rotation deal.
• Polls also show Netanyahu's right-wing bloc far ahead in a potential election match-up.

The bottom line: It will take a miracle to prevent an early election.

Go deeper: Gantz's "submarine affair" probe signals end of pact