Theodore Sasson is right that while the Conference of Presidents has, in recent years, ceased being the consensus institution it was created to be, admitting J Street as a member-organization is the appropriate thing to do.
J Street’s inclusion will contribute to the Conference’s claim to represent American Jewry—all of the big national organizations are already members (the ADL, AJC, AIPAC, the Jewish Council for Public Affairs, the Jewish Federations of North America). In addition, leaving J Street out of the communal tent because some consider it too partisan and left-wing ignores the fact that there are already several highly partisan member-groups from both ends of the spectrum (American Friends of Likud, the ZOA, JINSA, Ameinu, Americans for Peace Now).
But there’s another, more instrumental, reason to bring J Street in: it will bring its lobbying machine with it. J Street has close ties to the Democratic Party, including President Obama. Although far-right partisans have tried to tie being pro-Israel with being Republican, it’s a highly problematic and misleading equation. Nor is it an effective way to maintain the ability to advocate in a political system comprised of parties on both the right and the left. J Street also has a large, committed, and active grassroots organization that can be mobilized for advocacy efforts.
As a side note, that grassroots base would provide more legitimacy to the Conference since it incorporates a much larger portion of the Jewish community than some of the other organizations that are already members.
Communal consensus has broken down within the US Jewish community along political, religious, and ideological lines. Excluding J Street with only help harden those divisions, but including it will go some way to helping overcome them.