At AIPAC, [Steven J. Rosen] helped pioneer executive-branch lobbying, a style of advocacy that was not widespread when he began it in the mid- 1980s, but is now a routine complement to the more traditional lobbying of Congress. Before Rosen, AIPAC had believed that the way to alter American foreign policy was to get senators to sign a letter. His insight was that he could also affect the process by dealing with the staff-level bureaucrats in the executive branch who originated the policies.

Rosen could also be ruthless with his colleagues. He was among those behind the ouster of Douglas M. Bloomfield as AIPAC's chief congressional lobbyist in 1988 and helped remove other employees. "He was spooky, strange and not driven by love for Israel," said M.J. Rosenberg, a former AIPAC employee who tangled with Rosen. "I saw him as a power player, interested solely in power."

AIPAC and prosecutors dispute those assertions. "Rosen and [Keith Weissman] were dismissed because they engaged in conduct that was not part of their jobs, and because this conduct did not comport with the standards that AIPAC expects and requires of its employees," AIPAC spokesman Patrick Dorton said.