The question returns every presidential election year: Is the Jewish vote up for grabs?

For longer than anyone can remember, most American Jews have supported Democratic candidates, and quadrennial Republican hopes to break the trend have remained unfulfilled. The best the Republicans have done in the postwar era was in 1980, when Ronald Reagan captured 39 percent of the Jewish vote. Despite all the talk about his relations with the Rev. Jeremiah Wright and his alleged coolness toward Israel, Barack Obama won 78 percent of the Jewish vote in 2008.

Will 2012 be any different? A recent AJC poll of Jewish opinion provides an indication at this stage of the campaign. It suggests not only how many Jews are likely to vote Democratic or Republican, but which Jews. Conducted by Knowledge Networks, the survey included a representative sample of 1,074 respondents.

Looked at collectively, American Jewry seems just about as Democratic and liberal as ever. A majority of the respondents, 52 percent, say they are Democrats, 19 percent declare themselves Republicans, and 26 percent are independents — two-thirds of whom say they feel closer to the Democrats. Almost half — 46 percent — are liberal or lean liberal, while just 19 percent are conservative or lean conservative. The rest say they are moderates.

Asked for whom they would vote were the election held today, 61 percent answered Obama, 28 percent said presumed Republican nominee Mitt Romney, and the rest were undecided. Clearly, Jews are far more pro-Obama than the general population, among whom the two candidates are running neck and neck.

But Jewish opinion looks considerably more complicated when the sample is broken down by issue priorities.

The survey asked respondents to identify the three issues they consider most important in deciding their presidential vote. The one most often mentioned was the economy, listed by 80 percent. Within this group, the percentages supporting Obama and Romney are virtually identical to the overall Jewish breakdown. A pro-Obama tilt is even more pronounced among the 57 percent who chose health care as a key issue — which received the second-highest mention. Fully 72 percent of this group says it would vote for Obama, with just 19 percent backing Romney.

But the picture was different for roughly a quarter of the Jewish sample, which has other priorities. Among the 22 percent who cited U.S.-Israel relations, Romney had a plurality of 45 percent, vs. 42 percent for Obama. Similarly, the 26 percent of respondents who listed national security as a priority issue gave Romney a 44 percent plurality, with Obama getting 42 percent. And although Obama defeats Romney among the 15 percentthat cites Iran’s nuclear program as a priority, the gap was narrow, 48 to 46 percent.

Within the Jewish population, a group that is less enthusiastic about Obama than Jews as a whole are those who attend religious services once a week or more, a category with heavy Orthodox representation. Only 53 percent of them would vote for the president, 8 points lower than the overall percentage for Obama. Frequent synagogue-goers consider national security, the Iranian threat and Israel, rather than the economy, as top concerns, and are inclined to oppose Obama.

The survey also asked the undecideds whether they were leaning toward Obama or Romney, and found that 50 percent would choose Obama, while 39 percent would vote for Romney. Comprising the undecideds are 26 percent of the Orthodox, 10 percent of Conservative and 11 percent of Reform Jews.

Interestingly, Obama came out ahead with 47 percent of Orthodox votes to 22 percent for Romney, with 31 percent still undecided. Among Conservative undecideds, Obama gets 43 percent to Romney’s 56 percent, and for Reform Jews it’s 54 percent for Obama and 46 for Romney.

In the end, there is little likelihood of a mass transfer of Jewish support from the Democrats to the Republicans, but even a small, incremental erosion of Jewish support for Obama could make a difference in key swing states, such as Florida and Ohio.

Like other Americans, the undecided Jews will be heavily influenced by the direction of the economy, but also by security concerns, Iran and U.S.-Israel relations. And recalling 2008, when an economic collapse and a controversial Republican vice-presidential nominee played major roles, let’s not rule out the unexpected.

Mervyn Danker is Northern California regional director of the American Jewish Committee.