For some people, these are the last hopes for a Clinton presidency. “Faithless electors” are those individuals who do NOT vote for the candidate whom they pledged for but instead vote for another candidate; however, it is a rare occurrence. In the history of presidential elections, there have been only 157 “faithless electors” according to FairVote. This page from the National Archives gives a good overview as well as listing the states that require electors to vote for the pledged candidate that. This Washington Post article provides additional elucidation as does this page from the National Council of State Legislatures.
Who Are Faithless Electors?