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Lobbying the White House on behalf of Larry Summers for Federal Reserve chairman should been more aggressive and more negative on vice chair Janet Yellen, friends of the former Treasury secretary told CNBC.
The friends, who spoke on the condition of anonymity, also said the lobbying should have happened earlier.
The friends spoke to CNBC "Squawk Box" host Andrew Ross Sorkin, who was reporting at The Nantucket Project conference in the Massachusetts on Friday.
Summers was on the island to take part in the event.
(Read more: Yellen likely nominee after Summers withdrawal)
—By CNBC's "Squawk Box" with reporting from co-host 's Sorkin.