By Jeffrey Heller
JERUSALEM (Reuters) - When Benjamin Netanyahu first became Israel's leader two decades ago, few would have predicted a future in which he would be poised to pass founding father David Ben-Gurion as its longest-serving prime minister.
In a country where no single political party has ever won an outright majority in parliament, voters have often had to trudge back to the polling stations after coalition governments have imploded before the end of their four-year terms.
But weeks after "Bibi" Netanyahu marked a cumulative 10 years in power, a political reality is dawning: the right-wing 66-year-old may not be popular with most Israeli voters, but there's no one else strong enough to unseat him.
On paper, Netanyahu's hold on power barely adds up: his right-wing coalition rules with only a one-seat majority in the 120-member Knesset. Nearly every vote is a nail-biter.
And the majority of Israelis, according to an opinion poll last week, have grown weary of the blue-suited Likud party leader, with 51 percent saying they wouldn't want him to run in the next election, which isn't due until 2019.
But there's a catch: the survey, in the liberal Haaretz daily, also showed that voters haven't got much faith in any of the current line-up of opponents either.
So much so, that commentary accompanying the Haaretz poll said there would need to be a "Big Bang" - the creation of a new centrist alignment that might replace the so-far ineffective center-left opposition to Netanyahu.
Political pundits say that line-up could be led by former Netanyahu allies - Finance Minister Moshe Kahlon, who split from Likud to form his own party, and Gideon Saar, a former Likud minister who announced a break from politics in 2014 after feuding with the prime minister.
A retired military chief, Gabi Ashkenazi, is still in the political closet but has been touted as a potential partner.
Kahlon's price-slashing reform of the cellular phone market as communications minister five years ago was widely popular, Saar could attract Likud voters dissatisfied with Netanyahu, and Ashkenazi has the kind of security credentials the Israeli electorate has traditionally embraced.
Ofer Kenig, a researcher on political reform at the Israel Democracy Institute, a think-tank, said that while Netanyahu is not very popular, "he largely enjoys the lack of leadership in both his camp and the opposite camp".
Kenig is not convinced the perception of an "unbeatable Netanyahu", fueled by what he called the "big shock" dealt to the Israeli left and center by Likud's last-minute victory in the 2015 election, is true.
"Nevertheless, I think that in the last decade there is almost an automatic majority for the right-religious bloc and that it would require something special, a joining of forces in the center and left, in order to try to change that."
An earlier survey in the Jerusalem Post and Maariv newspapers hammered home the point: Netanyahu outpolled his main opposition rival, Zionist Union leader Isaac Herzog, by a 56 to 25 percent margin.
Within Netanyahu's coalition, Naftali Bennett, the youthful head of the ultranationalist Jewish Home party, trailed him in popularity by a 40 to 29 percent margin.
Only Ben-Gurion, who declared Israel's independence in 1948 and served as prime minister on and off until 1963, has led the country longer than "Bibi". Netanyahu, will break Ben-Gurion's 12-1/2-year record if he remains in office until Sept. 23, 2018, according to the Israel Democracy Institute.
To do so, the veteran politician must keep his government together. That has always been a struggle in Israel, but perhaps less so now: In the past, peace talks with the Palestinians have been a cause of coalition splits, but there haven't been any talks since 2014, and there are no signs of them resuming.
With world attention focused on hotter spots in the Middle East and Islamist militant bombings in Europe, Netanyahu has been moving ahead with settlement plans in the occupied West Bank. That is likely to appease ultranationalist political allies, helping to shore up his coalition.
And he is also burnishing his image as "Mr Security", playing on the fact that even if voters may not like him, they appear to trust him when it comes to tackling threats.
On Monday, a visibly relaxed Netanyahu visited Israeli military reservists in the occupied Golan Heights, choosing the occasion to let a secret out of the bag.
He confirmed numerous reports over several years that Israel has conducted dozens of air strikes across the nearby frontier with Syria against arms shipments to Hezbollah, the Iranian-backed guerrilla group that controls much of south Lebanon.
The disclosure, after Israel's refusal to acknowledge such attacks, perhaps out of desire not to provoke Hezbollah, came a day after he publicly put another security notch in his belt.
A half-year-long surge in Palestinian street attacks against Israelis is waning, he told his cabinet on Sunday, attributing the decline to "very firm action" by Israeli security forces.
It's that tough talk that appears to keep the gray-haired Netanyahu one step ahead, fending off his rivals even as they look for new ways to unseat him.
(Editing by Luke Baker and Giles Elgood)