Here is what the Washington Post had to say about how they identified NCPAC in a correction to their big NCPAC piece last Monday:
Between the first and second March 21 editions, a paragraph was dropped from a Style article on Joseph F. Steffen Jr., a former political aide to Maryland Gov. Robert L. Ehrlich Jr. The story described e-mails posted on the Web site FreeRepublic.com under the name NCPAC, which is short for National Conservative Political Action Committee. The paragraph that should have appeared said:
"Steffen confirmed to The Washington Post last month that he is NCPAC (pronounced 'nik-pak'). He canceled a meeting scheduled for this article and did not respond to further requests for comment. No one else could post messages as NCPAC without NCPAC sharing his password, according to a spokesman for FreeRepublic.com. NCPAC posted about a thousand messages between January 2004 and early last month. They were sprinkled with autobiographical asides that a reporter independently verified as facts of Steffen's life."
Sounds like they lurked here to prove NCPAC was Mr. Steffen and called him to confirm.