Critics accuse Mr. Khan of pandering to hard-line Islamists and naively seeing violent extremism as merely a reaction to the American military presence in neighboring Afghanistan.
That raised concern the violence could benefit hard-line Islamists and others who take a softer line toward the militants, like Sharif and Khan, because they were able to campaign more freely.
An FBI official said AbdulMutallab was included in TIDE after his father warned the U.S. Embassy in Nigeria of his son's hard-line beliefs and possible ties to militant Islamists.
An FBI official said AbdulMutallab was included in the U.S. government's Terrorist Identities Datamart Environment, or TIDE, after his father warned the U.S. Embassy in Nigeria of his son's hard-line beliefs and possible ties to militant Islamists.