Isaac Herzog is a scion of a rabbinical, military and political dynasty, but even supporters wonder whether he can topple “King Bibi.” (Jack Guez/AFP/Getty Images)

If he wins the upcoming elections, incumbent Benjamin Netanyahu will serve a historic fourth term as prime minister of Israel, earning his sobriquet “King Bibi.”

But there is a challenger to the coronation, the underdog of Israeli politics, a scion of rabbinical, military and political aristocracy: the dogged lawyer Isaac Herzog, who might deny his opponent another victory.

This is a rare event in recent Israeli politics. Polls ahead of the March 17 legislative elections show a contest that is too close to call. A win by Herzog would be a stunning reversal of fortunes for Israel’s ascendant hard-line right, whose members see themselves as partners with Netanyahu if he wins. In doctored photographs on social media, they’ve begun to depict Herzog wearing a Palestinian head scarf.

The victor will face a broken relationship with the White House and a lame-duck U.S. president; an assertive Palestinian leadership pushing war crimes charges against Israel before the United Nations; and a potential showdown with Iran over its nuclear ambitions.

[Read: U.S. officials, in blunt language, say Israel is distorting reality of Iran talks]

A woman passes a vandalized election campaign poster of Isaac Herzog and Tzipi Livni in Tel Aviv. In doctored photos on social media, some on the hard-line right are depicting Herzog in a Palestinian headscarf. (Abir Sultan/EPA)

On the surface, the two candidates are as different as can be. Netanyahu is warring with President Obama. Herzog seems to want to be President Obama: The Labor Party leader is campaigning on an Israeli version of “hope and change.”

Herzog’s billboards promise Israeli parents an extra teacher in each kindergarten classroom. Netanyahu warns about “the people who want to kill us.” He is fixated on the Iranian mullahs, who he says pose an existential threat to the Jewish state and places beyond.

Netanyahu is prepared to risk the ire of the White House and Democrats to make his case before a joint session of Congress on March 3. He believes that any treaty that allows Iran to hover at the threshold of nuclear breakout is “a bad deal.”

Herzog, on the other hand, says all Netanyahu has done is anger Israel’s closest ally. He said Netanyahu’s planned trip to Washington, without the invitation of the president, is a mistake that damages bipartisan support for Israel, which receives unwavering American backing and $3 billion in annual aid, including advanced weaponry.

On Iran, “I trust Obama to get a good deal,” Herzog has said.

“I agree that a nuclear Iran is extremely dangerous, and I believe that it must be prevented,” Herzog said in an interview. “No Israeli leader will accept a nuclear Iran. All options for me are still on the table,” including Israeli military strikes.

But rather than work against Obama or confront Secretary of State John F. Kerry and congressional Democrats, “I would rather hold intimate talks and renew the trust that is necessary between the United States and Israel,” Herzog said.

He declined to call Iran “an existential threat.”

“It is a big threat,” Herzog said. “That’s enough.”

All about Netanyahu

Pundits say the race is essentially a referendum on Netanyahu. The campaigns are filled with online parody ads and not much substance. The big news last week was the money Netanyahu and his wife spent on take-out food and maid service.

[Read: Israel’s Netanyahu spent $24,000 on takeout, and it’s causing a scandal]

The candidates have not debated and are unlikely to do so. No one is talking about the Israeli-Palestinian conflict, and the issue of Iran is seen through the optics of whether Netanyahu should speak to Congress — not what he might say about Iran.

Herzog’s supporters want change, but they are wary of him. Netanyahu’s voters want to keep to the course, even if they’re not sure where the prime minister is leading them.

Voters clearly have doubts about Herzog, who has been defined by Israeli media — and Netanyahu — as a nice guy but a small fry.

“Much hope rests on his small shoulders,” the columnist Asher Schechter wrote in the Israeli newspaper Haaretz, and Schechter is a Herzog supporter. He went on to compare the challenger to “a small animal that uses cunning and wit to survive in the jungle.”

The most recent poll for Israel’s Channel 10 news, conducted by a researcher at Tel Aviv University, found Netanyahu and Herzog tied for the number of seats their parties would win in parliament. But asked whom they preferred as prime minister, 44 percent of Israelis surveyed chose Netanyahu, compared with 36 percent for Herzog.

Herzog as expert manipulator

If “Bibi” Netanyahu is the baritone in the Israeli political opera, his challenger “Buji” Herzog is the alto, and a little nasal. Both are wickedly lampooned by Israeli satirists. On a popular weekly sketch show called “A Wonderful Land,” Bibi is the dark lord Emperor Palpatine from “Star Wars,”and Buji is a young Luke Skywalker with a flaccid lightsaber.

[Read: Israeli satirical TV show returns just in time for elections]

Netanyahu is arrogant, his supporters say, but they admire his swagger. He’s a tough guy in a tough neighborhood, they say. Polls suggest Israeli voters may be tired of Netanyahu, but many can’t quite imagine the prime minister’s office without him.

Netanyahu’s pitch is that he is the only adult in the room. His critics see a bully who spots threats everywhere and opportunities nowhere, who seeks to manage an unsustainable status quo rather than take Israel to the next place.

Herzog, the leader of the Labor Party, boasts of being a team player, a listener, a coalition builder. The 54-year-old has been surprising skeptics, and he promises to do so again in March.

“We have shown that Netanyahu is beatable,” he said in the interview.

Herzog won the leadership of the Labor Party last year in a bold stroke against an entrenched, popular politician.

“A tough election; no one gave me a goddamn chance,” he said. Then he buttressed his challenge against Netanyahu by forming a political partnership with former justice minister and peace negotiator Tzipi Livni, choosing her as a running mate.

“He appears to be this wimpy guy with the voice a bit too high, who has no security experience. But what Herzog offers us, what he is selling, is that he is in reality the master political manipulator,” said Yossi Alpher, an author and a former officer in the Mossad intelligence agency.

The rivals’ backgrounds

Netanyahu was born in Tel Aviv, the son of secular Jews. His father was a historian of Jews in Spain under Moors and Christians. He attended MIT and Harvard. He was a team leader of a special forces squad during his army days. Before becoming prime minister, Netanyahu served as Israeli ambassador to the United Nations and foreign minister.

Herzog also was born in Tel Aviv, the grandson of the chief rabbi of Israel. His father was a military general and the sixth president of Israel. Herzog attended Cornell and New York University. He served in the Israeli military intelligence corps and worked in the law firm established by his father, then later served as a minister of social welfare and tourism.

Retired Israeli general Omer Bar-Lev, a Herzog ally, dismisses the idea that Netanyahu’s security credentials trump his candidate’s.

“They both served, and let’s be honest, they both served at a very, very low level,” he said.

Bar-Lev said he believes Herzog, far from being weak or indecisive, would attack Iran.

“Consider Netanyahu,” he said. “For six years, the Iranian nuclear issue has been his top priority. He put all his efforts into this, and after six years, what has he achieved? A failure. A bad deal, from the Israeli perspective.”

If elected, Herzog vows his first task will be to repair relations with Washington.

“People of Israel understand much more than you think, and you can see how they are in total dislike of this clash or this tension with the United States,” he said.

Ruth Eglash contributed to this report.