WASHINGTON - Two days after John McCain told a leading pro-Israel lobby that he would toughen sanctions against Iran, Barack Obama assured the same group of his commitment to protecting Israel against the Iranian threat.
"I will do everything in my power to prevent Iran from obtaining a nuclear weapon," the presumptive Democratic presidential nominee told thousands of members of the American Israel Public Affairs Committee in Washington.
"Let there be no doubt: I will always keep the threat of military action on the table to defend our security and our ally Israel," he said.
Addressing AIPAC - long considered one of Washington's most influential lobbies - has become almost a requirement for presidential candidates seeking the Jewish vote. But there was an added imperative for Obama, who has battled accusations that he is overly sympathetic to the Palestinian cause and too willing to negotiate with Iran's president, Mahmoud Ahmadinejad.
McCain, the presumptive GOP nominee, has made the latter charge a centerpiece of his critique of Obama's qualifications to be president.
Yesterday, Obama gave a full-throated defense of his plan to engage Iran more directly, arguing that the Bush administration's policies have destabilized the Middle East and jeopardized both U.S. and Israeli security.
"There are those who would continue and intensify this failed status quo, ignoring eight years of accumulated evidence that our foreign policy is dangerously flawed," Obama said, taking a swipe at his Republican rival.
"I would be willing to lead tough and principled diplomacy with the appropriate Iranian leader at a time and place of my choosing," he continued. "Only recently have some come to think that diplomacy by definition cannot be tough. They forget the example of Truman, and Kennedy and Reagan. These presidents understood that diplomacy backed by real leverage was a fundamental tool of statecraft."
Obama drew frequent and sustained applause for such comments, but it was his repeated proclamations of support for Israel that evoked the biggest ovations. He cited his own youthful search for his roots to explain his admiration for the Jewish state, and he recalled that his great-uncle was among the U.S. soldiers who liberated the Buchenwald concentration camp in 1945.
Turning to the contemporary impasse in the Middle East, Obama criticized the Bush administration for neglecting the peace process. "I won't wait until the waning days of my presidency," he said. "I will take an active role, and make a personal commitment to do all I can to advance the cause of peace from the start of my administration."
Obama also talked of isolating Hamas, the militant group that controls the Palestinian government, and confronting Syria, which has provided support to Hamas. And he endorsed an "undivided" Jerusalem as Israel's capital, a position often associated with the right wing of Israeli politics.
"I wonder if he really means it," said Michael Oren, a senior fellow at the Shalem Center, an independent Israeli think tank. "Even Bush doesn't use the U-word. It may come back to haunt Obama if he wins."
Some Jewish voters are wary of Obama partly because his former pastor, the Rev. Jeremiah A. Wright Jr., praised the Black Muslim leader Louis Farrakhan, who has made anti-Semitic remarks. Obama disavowed Wright's intemperate remarks and later resigned from that church.
Obama also cited e-mails "filled with tall tales and dire warnings about a certain candidate for president," a reference to false accusations that he is a Muslim with a hidden agenda. "Let me know if you see this guy named Barack Obama, because he sounds pretty scary," he said.
Obama clearly impressed some in the massive hall.
"He had me in tears, this feeling for an understanding of Israel's predicament," said Leonard Eisenfeld, a Connecticut pediatrician whose son was killed in a Hamas bus bombing in Jerusalem in 1996. He said he respects McCain but is now more open to Obama, calling him a "good soul" in Yiddish.
But Evelyn Mottsman of Pittsburgh said it "disturbs a lot of people that he thinks diplomacy is possible" with Iran.
And one Palestinian official expressed dismay because Obama "said that Jerusalem would remain undivided as the capital of Israel."
"If he means that, that means closing all doors for peace," Palestinian negotiator Saeb Erekat told the Associated Press in Jerusalem. "We had hoped that under the banner of change, Mr. Obama would have said that east Jerusalem would be the capital of the Palestinian state."
Noam N. Levey writes for the Los Angeles Times. The Associated Press contributed to this article.