TEL AVIV, Israel — Gadi Eisenkot is as low-key as Benjamin Netanyahu is bombastic. He's a political novice up against the longest-serving, most politically savvy prime minister in Israel's history.

And yet, on the eve of Tuesday's elections, Eisenkot poses the most serious threat to Netanyahu's hold on power in years.

Why it matters: A victory by the Yashar party leader would upend Israeli politics and could reset the country's strained relationships abroad.

The intrigue: The contrast between the two top contenders could hardly be sharper.

Their roots: Eisenkot, the son of Moroccan Jewish immigrants, grew up in Eilat, Israel's southernmost city.

If he wins, Eisenkot will be the first prime minister of Moroccan descent in Israel's history.

Their military backgrounds: Netanyahu served in the Israel Defense Forces' elite special forces unit "Sayeret Matkal" and later went into business and politics.

Eisenkot joined the IDF Golani infantry brigade and rose through its ranks as a combat commander until…