I am at the AIPAC conference today waiting for President Obama to speak. This is the largest gathering of the American Israel Public Affairs Committee to date, with about 10,000 people registered. It may be the most misunderstood and defamed group in the country.

It is not a Jewish group. Christians belong and advocate on the issues AIPAC cares about, namely a secure Israel and a warm U.S.-Israel relationship. It does not advocate for Israel, but for a robust U.S.-Israel relationship, which its members (correctly, in my view) see as vital to the security and the character of America. It does not endorse candidates or give to political candidates (though many of its members are active in electoral politics). It lobbies on aid to Israel and is influential on Iran sanctions and other issues relating to our democratic allies security needs. It is not the largest Zionist organization. That distinction goes to Christians United for Israel.

It is also not “right wing” or “hawkish” or “conservative.” Josh Block, a Democratic activist and former AIPAC spokesman, e-mailed me:

AIPAC is a bipartisan organization whose members — Americans of all faiths and backgrounds — support the U.S.-Israel relationship because it is good for America, our values and our national security. While it is true that the membership is overwhelmingly made up of Democrats — not surprising, since most Jews are Democrats — the organization is neither liberal or conservative, not left or right. Rather, it is an umbrella pro-Israel organization whose membership holds a wide diversity of views, but agrees on one thing — along with 80+ percent of American voters, who believe Israel is one of our closest and most important friends in the world.

And that we ought to treat them that way.

Frankly, many Jews think AIPAC has been insufficiently combative with the Obama administration. And there are groups that engage in more vocal criticism of the president, such as the Republican Jewish Coalition and the Emergency Committee for Israel.

In a sense AIPAC mirrored the bipartisan U.S. policy and the tone of every administration since the founding of the Jewish state, until the current one.

The president blew it on Thursday. Obama articulated a major shift in U.S. policy at odds with prior administrations and agreements that the United States is party to or helped negotiate. Some have called this “no big deal” or “no big change” from past presidents’ positions. This — to the Israelis, the American Jewish community, and close observers and participants in the peace process — is inaccurate. In fact, the Obama team knew it was a big deal when Secretary of State Hillary Clinton belatedly called Prime Minister Binyamin Netanyahu to explain what Obama was about to spring on him.

Obama made the 1967 borders with land swaps U.S. policy. He did not, as did President George W. Bush in words and in an exchange of letters with then-Prime Minister Ariel Sharon (who relied on this understanding and undertook a withdrawal from the Gaza Strip and other concessions in the West Bank), say that the 1949 Armistice Lines were not attainable. He described borders for the Palestinian state (contiguous with Jordan) that ignore mutual understandings about the need to maintain a security position in the Jordan Valley. He did not, as every president previously did, promise to veto a Security Council resolution bypassing the bilateral negotiation process that has been a fixture of international law since 1967. He did not state that he would abide by U.S. law and cut off a government that contained Hamas elements. In sum, it certainly is “a big change.”

In the lack of coordination with our ally and the distinctly pro-Palestinian slant, Obama confirms his distinction as the president least sympathetic to Israel and most disruptive of the peace process.

That was the background to Friday’s extraordinary scene at the White House. A stone-faced Obama with head in hand (disrespectful, if not hostile, body language) listened to Netanyahu correct the record, as a parent or teacher would instruct a misguided or ignorant minor. (One who perhaps doesn’t know what the Knesset is.) An excerpt illustrates Netanyahu’s rebuttal, describing some “basic realities”:

The first is that while Israel is prepared to make generous compromises for peace, it cannot go back to the 1967 lines — because these lines are indefensible; because they don’t take into account certain changes that have taken place on the ground, demographic changes that have taken place over the last 44 years.

Remember that, before 1967, Israel was all of nine miles wide. It was half the width of the Washington Beltway. And these were not the boundaries of peace; they were the boundaries of repeated wars, because the attack on Israel was so attractive.

So we can’t go back to those indefensible lines, and we’re going to have to have a long-term military presence along the Jordan.

He also reminded Obama that not giving in to the Palestinians’ demand to “return” (millions never lived there in the first place) is essential to the Jewish state:

The Arab attack in 1948 on Israel resulted in two refugee problems — Palestinian refugee problem and Jewish refugees, roughly the same number, who were expelled from Arab lands. Now, tiny Israel absorbed the Jewish refugees, but the vast Arab world refused to absorb the Palestinian refugees. Now, 63 years later, the Palestinians come to us and they say to Israel, accept the grandchildren, really, and the great-grandchildren of these refugees, thereby wiping out Israel’s future as a Jewish state.

So it’s not going to happen. Everybody knows it’s not going to happen. And I think it’s time to tell the Palestinians forthrightly it’s not going to happen.

But Obama isn’t going to prejudge that issue like he did Israel’s borders. Every previous American president would have (or has) stated precisely what Netanyahu did. Only this president has sought to change the rules under which Israel, the United States and the rest of the world have operated for 63 years. Obama apparently takes Jewish votes so for granted that he thinks he can say or do just about anything without denting their support or enthusiasm.

The president is now estranged on this issue from the American people (who remain exceptionally pro-Israel), Congress (which ratified overwhelmingly the Bush-Sharon 2004 letters, which are in sync with Netanyahu’s comments) and the closest U.S. ally in the Middle East.

Soon Obama will enter the room. I suspect many of the attendees share the view of Rep. Theodore E. Deutch (D-Fla.), who put out a statement that read in part: “Should Israel find a partner for peace who is willing to join Prime Minister Netanyahu at the negotiating table, Israel cannot be expected to make any territorial concessions that do not acknowledge the reality on the ground. The 1967 borders are indefensible.”

If Obama had said that, he wouldn’t be in the current fix. The crowd’s reaction (after explicit pleas by AIPAC’s executive director to be courteous, something never before required for a president) and Obama’s comments are a decisive moment for him, the U.S- Israel relationship and the American Jewish community. The high tensions speak volumes about how Obama is perceived by friends of Israel.