Director of National Intelligence James Clapper testifies during a hearing before Senate Select Intelligence Committee on Wednesday. Alex Wong/Getty Images hide caption

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National Intelligence Director James Clapper waits for a hearing of the Senate Judiciary on Wednesday. Brendan Smialowski/AFP/Getty Images hide caption

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Director of National Intelligence James Clapper has apologized for a "clearly erroneous" response to a question about surveillance on Americans. The question was asked before the Senate Intelligence Committee in March. Susan Walsh/AP hide caption

itoggle caption Susan Walsh/AP