President Barack Obama hugs Mari Copeny, 8, backstage at Northwestern High School in Flint, Mich., May 4, 2016. Mari wrote a letter to the President about the Flint water crisis.

President Barack Obama hugs Mari Copeny, 8, backstage at Northwestern High School in Flint, Mich., May 4, 2016. Mari wrote a letter to the President about the Flint water crisis.

President Barack Obama hugs a woman in the crowd after addressing the Labor Day celebration in Detroit, Mich., Sept. 5, 2011.

President Barack Obama hugs a woman in the crowd after addressing the Labor Day celebration in Detroit, Mich., Sept. 5, 2011.

President Barack Obama greets a man in the crowd after addressing the Labor Day celebration in Detroit, Mich., Sept. 5, 2011.

President Barack Obama greets a man in the crowd after addressing the Labor Day celebration in Detroit, Mich., Sept. 5, 2011.

President Barack Obama exits the stage with University of Michigan president Mary Sue Coleman after delivering the commencement address to University of Michigan graduates at Michigan Stadium, in Ann Arbor, Mich., Saturday, May 1, 2010.

President Barack Obama exits the stage with University of Michigan president Mary Sue Coleman after delivering the commencement address to University of Michigan graduates at Michigan Stadium, in Ann Arbor, Mich., Saturday, May 1, 2010.

President Barack Obama touches the sign above the locker room door at Michigan Stadium, before giving the commencement address to University of Michigan graduates in Ann Arbor, Mich., Saturday, May 1, 2010.

President Barack Obama touches the sign above the locker room door at Michigan Stadium, before giving the commencement address to University of Michigan graduates in Ann Arbor, Mich., Saturday, May 1, 2010.