J Street wrapped up its first national conference with more than 700 activists pressing their congressmen on their agenda throughout the day Wednesday.

The effect that lobbying will have on US policy remains to be seen. But this week the 18-month-old, self-described "pro-Israel, pro-peace" organization made clear that it had emerged as a presence in Washington.

It held a coming-out party larger than the annual events of many other longstanding Jewish and Israel-oriented organizations. And despite criticism of the group from some segments of the Jewish community and some high-profile rejections and cancellations, the lobby still garnered the attendance of high-placed administration officials, dozens of members of Congress, international diplomats and overflowing numbers of activists clearly energized and excited by the to-do.

Perhaps the biggest seal of approval came from National Security Adviser James Jones, who not only praised the conference, but indicated it was here to stay.

"Congratulations on this great conference," he told a roaring crowd of 1,500. "You can be sure that this administration will be represented at all other future J Street conferences."

Jones wasn't the only major figure to address the audience of activists, politicians and policymakers. The capstone gala on Tuesday night featured a video address from King Abdullah of Jordan, who congratulated the group and backed its call for a two-state solution.

A Jordanian diplomat stressed to The Jerusalem Post that this message was the same as those Abdullah had delivered to other Jewish groups, and in keeping with his longstanding commitment to reaching out to the Jewish community. The official noted that Abdullah had participated in other organizations' conferences and met with Jewish leaders from a wide range of groups on trips to Washington.

But a European diplomat at the event who spoke to the Post was more pointed in his backing for this particular group. He said coming to the gala was important because "we want to show our support" for the group and its approach to the Middle East.

J Street has emphasized the importance of immediately reaching a two-state solution and its preference for diplomacy in resolving conflict. Some of its positions in favor of a settlement freeze and skeptical of Iran sanctions, among others, have put it at odds with the Israeli government. Israeli Ambassador to Washington Michael Oren turned down his invitation, with an embassy spokesman explaining that the organization took positions that could "impair" Israel's interests.

That response, according to some Capitol Hill observers, helped turn away some dozen of the 160 members of Congress who had originally lent their names to the gala's host committee. Some of the others who withdrew said it was because they hadn't realized their staff had signed them up.

Several conservative bloggers and other political allies also spoke out against the event, and Stand With Us sent a letter to members of Congress on the host committee, saying, "We are troubled because their [J Street's] positions seem to undermine Israel and its search for peace with security. Their views may also contribute to anti-Israel biases and misinformation."

In the face of those objections, 44 members showed up to the gala dinner, according to J Street.

And while one of the bigger-name speakers, Senate Foreign Relations Committee Chairman John Kerry, was a no-show, House Foreign Affairs Committee Chairman Howard Berman did attend the gala, and the dinner's keynote speaker, Chuck Hagel, went from being a former Republican senator to the new co-chair of the White House's Intelligence Advisory Board on Wednesday.

In addition, five members of Congress spoke at plenary sessions, and Florida Democratic Representative Debbie Wasserman Schultz, who has a reputation for being a strong advocate for Israel on Capitol Hill, addressed participants at a closed-door VIP reception.

"Debbie Wasserman Schultz, I'm sure, wanted to help give some cover to the administration on J Street - by giving her hecsher [kosher certification], she helps relieve pressure on the White House for being so cozy with J Street," said one mainstream Jewish official of her participation, which raised some eyebrows given the debate in the Jewish community over the nature of the group.

Wasserman Schultz would not talk to the Post when approached at the conference.

Though the congressional lineup and 1,500 attendees was dwarfed by the annual American Israel Public Affairs Committee convention - which drew over half the 535 members of the House and Senate and 75 diplomats this year - it was a strong showing for the new kid on the block. "Impressive" was a common word on the lips of participants and observers.

J Street does not publicly describe itself as a counter to AIPAC, the established lobbying powerhouse on American policy toward Israel. But the leadership's emphasis on changing what it means to be pro-Israel and where American Jews are seen as standing on US-Israel policy is commonly viewed as a clear challenge to the decades-old AIPAC.

AIPAC itself seemed to avoid a direct showdown over the conference.

"I am very confident that AIPAC purposely did not send signals of any kind to Congressmen about signing up or not signing up for the J Street conference. AIPAC took a very low-key approach," said one Jewish organizational leader with ties on Capitol Hill, adding that if AIPAC had contacted members of Congress to ask that they not participate in the J Street conference, there was "no way" so many would have come or served on the host committee.

"AIPAC did not tell any member anything like that. Period," said one source close to AIPAC.

In at least one incident, though, people associated with AIPAC were among those who raised questions about JTA Washington reporter Ron Kampeas moderating a J Street panel which he was then pulled out of, according to individuals familiar with the situation.