WASHINGTON — It’s a familiar calculus in the relationship between the Jewish community and the Bush administration: a social issue that divides the country 50-50 has the Jewish community split 75-25 against where President Bush stands.

On Monday, Bush strongly endorsed the federal marriage amendment to the U.S. Constitution, which would effectively ban gay marriage.

“Marriage is the most fundamental institution of civilization, and it should not be redefined by activist judges,” Bush said after meeting with supporters of the constitutional amendment. He was referring to the 2004 decision by the Massachusetts Supreme Court to recognize same-sex marriages.

The bill, which was likely to be considered by the U.S. Senate on Wednesday, has virtually no chance of passing. Constitutional amendments need 67 of the 100 Senate votes to pass, and no one expects the vote to break 55.

That makes it a win-win for Bush in his effort to keep evangelical conservatives on board ahead of the November midterm congressional elections. The reasoning is that the amendment will still resonate with the Republicans’ conservative base five months from now, but will probably have disappeared from the memories of social moderates who may lean Republican for other reasons.

However, Jewish Republicans, who have been trying to lure Jews away from their solid 3-to-1 support for Democrats, might have been dealt a blow, at least according to the amendment’s opponents.

“It’s unclear to me how the Republican Party will gain ground in the Jewish community by bringing forth a centerpiece of the religious right’s agenda,” said Mark Pelavin, associate director of the Reform movement’s Religious Action Center. “For a large section of the Jewish community, this is an issue of fundamental rights, and they will be watching closely to see how their senators vote.”

The Reform and Reconstructionist movements oppose the amendment. On Tuesday, the Conservative movement’s leadership joined in the opposition, in a statement that referred to a 2003 United Synagogue resolution opposing any such discrimination. Also in opposition are major Jewish civil liberties groups, including the American Jewish Committee and the Anti-Defamation League.

The National Council of Jewish Women has taken a lead in opposing the legislation, organizing clerical lobbying against it and leading an alliance of liberal Jewish groups in urging senators to vote it down. Orthodox groups, led by the Orthodox Union and Agudath Israel of America, support the amendment.

The most recent polling on the issue, by Gallup, found 50 percent of Americans in favor of the amendment and 47 percent opposed. A 2004 American Jewish Committee survey of American Jews found 24 percent in favor and 74 percent opposed.

Jewish supporters of the amendment suggested they would sell the amendment to the Jewish community as one that would guarantee religious freedoms.

Proponents of gay marriage were “pursuing a deliberate plan of litigation and political pressure which will not only redefine marriage, but will follow from that to threaten the first freedom enshrined in the First Amendment — religious liberty,” said Nathan Diament, the director of the Washington office of the Orthodox Union.

Diament, the only Jewish participant at the meeting with Bush on Monday, told JTA that the Massachusetts ruling already had a negative impact on religious freedom. He cited as example the state’s Roman Catholic Church decision to drop out of the adoption business because it would be required to consider gay couples as parents.

“They’re trying to impose their position on society at large,” he said of proponents of gay marriage. “How a society defines marriage affects everybody.”

That view had some backing from at least one Jewish civil rights group, the American Jewish Congress.

Marc Stern, the AJCongress’ general counsel, cited the example of an Orthodox kosher caterer who could face a lawsuit for refusing to cater a same-sex wedding.

A successful compromise would “recognize the marriages in the context of a secular economy, for instance by not discriminating on domestic partner benefits, but it would not force people to act in areas they find morally reprehensible,” Stern told JTA.

Chai Feldblum, a Georgetown University law professor and an activist for gay rights, said such arguments had no place in the public arena.

“There are lots of ways in which a religious organization can run its business as it wishes. Rabbis don’t have to perform a marriage that they don’t agree with; a religious organization does not have to allow lesbians as rabbis,” said Feldblum.

“The problem is when religious organizations are operating in the public arena, with lunch banks, day camps, shelters. Then it’s very difficult to allow a religious organization to go against the public policy of the state.”

Feldblum, who grew up Orthodox, said she has compassion for her observant opponents. “The world is shifting beneath their feet,” she said.

Republican Jewish spokesmen turned down requests for comment, but the amendment was not likely to help their efforts to appeal to Jews on domestic issues.

The emphasis before the 2004 election on Bush’s friendship with Israel and his tough reputation on security issues failed to make much of a dent on the Jewish Republican vote, which crept up to between 23 percent and 25 percent from about 19 percent in 2000.

Since then, Jewish Republicans have learned the lesson of emphasizing foreign policy too much and have carefully calibrated a social message designed to appeal to younger Jews. In Jewish newspaper advertisements and in stump speeches, Bush’s pro-business record is pitched to Jewish voters who may be more fiscally conservative than their parents.

And spokesmen like party chairman Ken Mehlman, who is Jewish, bluntly acknowledge to Jews that the Democrats were on the right side of history when they backed civil rights in the 1960s; but they say that Bush has inherited that mantle with his efforts to promote democracy abroad and force education reforms at home.

The most prominent Jewish Republican, Sen. Arlen Specter, R-Pa., chairman of the Senate Judiciary Committee, said he would vote against the amendment. He cited classic Republican small government philosophy: Government “ought to be kept off our backs, out of our pocketbooks and out of our bedrooms,” Specter said, according to The New York Times.

Democrats said the marriage amendment would help cripple such efforts.

“The Republicans are saddled with an agenda that’s horrific to the vast majority of American Jews,” said Ira Forman, the executive director of the National Jewish Democratic Council.

Supporters of the amendment said they believed momentum was on their side. A similar effort in 2004 garnered just 48 Senate votes; this effort will top 50, they believe.

Abba Cohen, the Washington director of Agudath Israel of America, said he believed all Americans would eventually internalize the amendment’s moral arguments.

“This battle will be won in stages,” he said. “It takes time for the nation to fully absorb the implications of allowing same-sex marriage and the effect it will have on traditional families.”

Pelavin of the Reform movement said his impression was that time was on the side of opponents of the amendment.

“This isn’t a fight that we picked. This is a fight that the president and the Republican leadership have picked,” he said. “This is an issue of fairness.”