Top Democrats have joined a number of Republicans in challenging President Obama’s policy toward Israel, further exposing rifts that the White House and its allies will seek to mend before next year’s election.

The differences, on display as senior lawmakers addressed a pro-Israel group late Monday and Tuesday, stem from Obama’s calls in recent days for any peace deal between Israel and the Palestinians to be based on boundaries that existed before the 1967 Arab-Israeli war, combined with “mutually agreed swaps” of territory.

Senate Majority Leader Harry M. Reid (Nev.), House Minority Whip Steny H. Hoyer (Md.) and other Democrats appeared to reject the president’s reference to the 1967 lines in his latest attempt to nudge along peace talks, thinking that he was giving away too much, too soon.

White House officials say Obama’s assertion did not reflect a shift in U.S. policy. But the president’s comments touched a nerve among pro-Israel activists, drew a rare Oval Office rebuke from Is­raeli Prime Minister Binyamin Netanyahu and instantly became a litmus test in domestic American politics.

Now Obama — whom critics often accuse of employing a play-it-safe governing style in which he waits for others to take the lead — is largely isolated politically in raising the issue of boundaries.

By this week, White House aides were reaching out to Israel supporters in the Jewish community to try to ease concerns, according to people familiar with the effort. The White House has arranged a conference call with Jewish leaders and contacted others for advice on repairing ties.

The political uproar, coming as Netanyahu received a bipartisan hero’s welcome Tuesday for a speech to Congress, underscored the careful calculations being made by leaders in both parties.

Democrats and Obama must balance the need to pursue delicate international diplomacy while retaining the party’s traditional support among Jewish campaign donors and voters, particularly in competitive states such as Florida, Ohio and Pennsylvania. The party’s liberal base, however, is divided, with many on the left urging more concessions by Israel.

Republicans increasingly consider Israel a core issue that can unify sometimes disparate party factions, with evangelical voters and foreign policy hawks alike emerging as some of the Jewish state’s most vocal U.S. backers.

Netanyahu, who since Thursday has repeatedly called the 1967 borders “indefensible,” helped set the stage for the torrent of White House criticism.

His response was quickly followed by criticism from Republicans vying to take on Obama next year. Former Massachusetts governor Mitt Romney, the presumed GOP front-runner, accused the president of throwing Israel “under the bus.” Former Minnesota governor Tim Pawlenty said Obama had made a “mistaken and very dangerous demand.”

The pressure from Republicans and fellow Democrats leaves the White House and top political aides with the added task of making amends with Israel backers by touting Obama’s history of support for that nation.

Among the prominent Israel supporters upon whom Obama has relied for advice are Lee Rosenberg, president of the American Israel Public Affairs Committee (AIPAC), and Alan Solow, who will leave his post as chairman of the Conference of Presidents of Major American Jewish Organizations next month. Both have been key behind-the-scenes advocates for Obama in reassuring skeptical backers.

This week, the president’s newly chosen national Democratic Party chairman, Rep. Debbie Wasserman Schultz, signaled that she, too, will serve as an emissary. Her South Florida district is home
to one of the country’s biggest Jewish populations, a place where Obama’s 2008 campaign tapped prominent Jewish lawmakers and local elected officials to visit synagogues and community centers and debunk rumors that Obama is a Muslim and anti-Israel.

“As a Jewish member of Congress who cares deeply about preserving Israel as a Jewish, democratic state, I am proud that President Obama spoke forcefully about continuing the United States’ strong and stalwart support of Israel,” Wasserman Schultz said in a written statement.

As part of their defense, a number of White House allies said Tuesday the political row had been fueled by Netanyahu, who seized on Obama’s reference to the 1967 lines but glossed over his additional point regarding land swaps.

Appearing irritated by the controversy, Obama said in his own speech to AIPAC on Sunday that his views had been “misrepresented several times.”

“Let me reaffirm what ‘1967 lines with mutually agreed swaps’ means,” Obama said, sounding exasperated. “By definition, it means that the parties themselves — Israelis and Palestinians — will negotiate a border that is different than the one that existed on June 4, 1967. That’s what ‘mutually agreed-upon swaps’ means. It is a well-known formula to all who have worked on this issue for a generation.” Obama went on to play down his remarks, saying “there was nothing particularly original in my proposal.”

Even so, he tried to portray his position as a sign of political courage, while also offering a subtle reminder that two of his closest advisers, Rahm Emanuel and David Axelrod, are Jewish. “I know very well that the easy thing to do, particularly for a president preparing for reelection, is to avoid any controversy,” he said. “I don’t need Rahm to tell me that. Don’t need Axelrod to tell me that.”

But between his Thursday speech, which was aimed in part at an Arab audience, and his Sunday address to AIPAC, Obama shifted some of his rhetoric toward the Israeli position. For instance, he referred to the Islamist militant group Hamas more directly as a “terrorist organization.”

Several experts said the president’s stance on boundaries was in line with past U.S. policy, albeit stated more bluntly. But some said it marked a significant shift, at least in tone, that Obama seemed open to an even swap of territory while deferring the more emotional questions of dealing with Jerusalem and the future rights of Palestinian refugees.

“He has shown a willingness to use political capital in pushing forward ideas that are not always going to be what people want to hear,” said David Makovsky, an analyst at the Washington Institute for Near East Policy, who co-wrote a book in 2008 with Obama adviser Dennis Ross that suggested a land swap and waiting on Jerusalem and refugees.

Makovsky noted that Obama received about eight in 10 Jewish votes in 2008, and that “many of those people who voted for him understand some of the positions that he has articulated,” such as his argument that further delays risk undermining Israel’s security and emboldening extremists.

Still, some Jewish Democrats said they remain concerned. One major party donor who attended AIPAC described a sense of “disappointment” in the hall about Obama’s remarks.

Reid said late Monday night at AIPAC that “no one should set premature parameters about borders, about building or about anything else.” Hoyer said negotiations must begin “without preconditions.” And Sen. Robert P. Casey Jr. (D-Pa.), drew applause Tuesday when he said Israel’s borders “ must be determined by parties on the ground.”