The United States is officially neutral in Tuesday's Israeli election but Benjamin Netanyahu is seen as the least appealing choice for prime minister to bolster the Obama administration's Middle East peace efforts.
Polls show Israelis leaning right after last month's war in Gaza and Netanyahu's conservative Likud Party likely to beat centrist Kadima, led by Foreign Minister Tzipi Livni. A far-right party led by former Netanyahu aide Avigdor Lieberman also is expected to do well.
"I think Netanyahu is going to have trouble working with this administration," said Ned Walker, who was U.S. ambassador to Israel during Netanyahu's last term as prime minister from 1996-1999. His views are "not consistent with the way the (Obama) administration has been talking so far," Walker said.
Netanyahu, who has vowed a tougher line on Palestinians, would be unlikely to want to move fast on U.S. President Barack Obama's pledge to restart U.S.-mediated peace talks.
The Likud leader also has a history of fractious relations with the last Democratic administration under President Bill Clinton, whose wife Hillary Clinton is now U.S. secretary of state and will deal closely with the new Israeli leader.
"Clinton washed his hands of Netanyahu," Walker said. "I don't know whether that will have an effect on Secretary Clinton. But he (Netanyahu) has to be aware of just how important the U.S. relationship with Israel is and that there are limits."
An easier electoral choice for the Obama administration would be Livni, who has led Palestinian statehood negotiations on behalf of the Israelis.
"There is no question that Livni seems to be more conciliatory," said Middle East expert Shibley Telhami of the University of Maryland.
Peace negotiations bogged down under the Bush administration and came to a halt when Israel launched a three-week offensive in Gaza in December to stop rockets fired on Israel by the militant group Hamas.
US-led efforts already are stymied by fragmented Palestinian politics. Hamas, which the United States considers a terrorist group, rules Gaza while the West Bank is controlled by Western-backed Palestinian President Mahmoud Abbas.
Telhami said conventional wisdom was that Netanyahu was more interested in Syrian-Israeli talks than Palestinian statehood negotiations, which Arab leaders are pushing the United States to mediate and make a priority.
No matter who wins on Tuesday, the climate for peace talks has been soured by the Gaza crisis, said Marina Ottaway, director of the Middle East program for the Carnegie Endowment for International Peace.
"Even if by any miracle Kadima (Livni's party) came out ahead, it would not make a lot of difference," she said. "There is a mood that prevails in political circles in Israel that this is not a time to make concessions but to take a hard line."
Daniel Levy, a senior fellow of the New America Foundation, said the real question was not who won the Israeli election but how Washington tackled the Arab-Israeli issue overall.
"What matters much more is whether there is a rethink in Washington and that should apply no matter who is in power."
How to handle Hamas and getting a sustainable truce in Gaza are key issues for the Obama administration. The thorny problem of Jewish settlements in the West Bank and Netanyahu's vow not to clamp down on them also will test the White House.
"In the short-term it matters a lot who wins in Israel," Telhami said. "Netanyahu has already said he will not freeze settlement building and that is a huge issue."
If the Obama administration did not act firmly on settlements, Ottaway said it would lose credibility with Arab allies who felt the Bush administration gave the Israelis the green light and were not seen as being tough enough.
So far, the Obama administration has given no signs of any shift in the Bush administration's approach to Israel. Caution has been the watchword as Clinton grapples with her new job.
"At this point the administration is not settled in yet. The Israeli election will force them to clarify the process by which they make policy in this region very quickly," Telhami said.