UMM AL-FAHM, Israel — With three weeks to go, the Israeli election is so close that Arab voters, who make up only a fifth of the population, could help bring Prime Minister Benjamin Netanyahu’s long career to an abrupt end.

Mr. Netanyahu has been fanning the flames of anti-Arab sentiment almost daily.

He has warned Israelis that his main challenger, the retired army chief Benny Gantz, would “hand over parts of the homeland to the Arabs” and that he would make alliances with Arab parties that “want to destroy” Israel. Mr. Netanyahu has also joined forces with a racist faction whose leaders support expelling Arab citizens and call them “the enemy.”

Such appeals have worked for Mr. Netanyahu in the past. This time they might backfire.

Small Arab communities like the Druze, who prize their loyalty to the state and often vote for right-wing parties, show signs of deserting Mr. Netanyahu en masse, according to a new poll from the University of Maryland. The poll also suggests that Mr. Netanyahu’s racial provocations may spur turnout among Arab voters motivated to usher him out of office.

[Read our overview of the Israel elections.]

If the race between Mr. Gantz’s Blue and White party and Mr. Netanyahu’s Likud remains a nail-biter, the swing of a single seat in Parliament could be decisive.