Two notes that might help in searching for this:
1. I'm finding references to Wilson meeting Kristof at a meeting of the Senate Democratic Policy Committee. From the big Vanity Fair article:
In early May, Wilson and Plame attended a conference sponsored by the Senate Democratic Policy Committee, at which Wilson spoke about Iraq; one of the other panelists was the New York Times journalist Nicholas Kristof. Over breakfast the next morning with Kristof and his wife, Wilson told about his trip to Niger and said Kristof could write about it, but not name him.
2. However, the meeting where the Democrats plotted how to undermine confidence in Bush may have been a meeting of the Democratic National Committee:
Dems plan to undermine America to beat Bush
Capitol Hill Blue obtained a copy of the talking points when the Democratic National Committee sent them to a news outlet recently acquired by CHBs parent company.
Obviously, I conflated the two. However, this May meeting apparently afforded the Democrats an opportunity to further the program they agreed to undertake in January.
Consequently, we have a nexus for the plot. Wilson, Kristof, a bunch of Democrat pols (is Schumer on this committee, I wonder). And, within days, things begin to happen...
...Kristof "leaks" Wilson's report (anonymously)
...Somebody identified as "a CIA agent" leaks to the BBC.
...Pincus and the WaPo gets on the scent.
...Wilson gets an op-ed in the NYT.
...and they're off and running at Pimlico...