According to iVoteIsrael, there are almost 160,000 potential voters in Israel. The group estimates that half of them cast absentee ballots this year, up from 20,000 in 2008.
"Jews tend to vote in America more than other communities, so it not's surprising that when they come over, their turnout remains high," said Eli Pieprz, the group's director.
It is unclear what impact the American expatriate votes will have. Most immigrants come from the New York area, which appears to be solidly Democratic this year. But there are sizeable communities from swing states like Ohio and Florida.
In the United States, Obama won 78 percent of the Jewish vote in 2008, according to exit polls at the time. Recent polls show the president down as much as 10 percentage points because of economic and foreign policy concerns, but by and large, American Jews remain firmly in the liberal camp that backs Obama — unlike American immigrants in Israel.
Jerusalem resident Bryna Franklin, a former Democrats Abroad-Israel chair, appears in a pro-Romney ad, saying that the special relationship between America and Israel doesn't exist anymore.
"Forget that you voted for Democrats since you've been knee high to a grasshopper," she says. "I'm urging American Jews to switch sides and vote for Romney as president."
Kory Bardash, the co-chair of Republicans Abroad-Israel, said Franklin's transition is one of many he's seen in Israel over the past few years.
But Sheldon Schorer, a leading member of Democrats Abroad-Israel, claimed that American votes in Israel parallel the votes of Jewish voters in America.
"Sure, Obama and Netanyahu might not have a warm relationship, but whether they go out on double dates to the movies and eat Chinese food together isn't of interest," he said.