Supporters reach out to touch the hand of democratic presidential candidate Senator Barack Obama (D-IL) after he spoke at a rally in Dallas, Texas February 20, 2008. REUTERS/Jessica Rinaldi

Students listen to remarks by U.S. President Barack Obama at Lehman College in New York May 4, 2015. During his remarks Monday Obama announced the creation of the new nonprofit organization My Brother's Keeper Alliance to help minority youth. REUTERS/Jonathan Ernst - RTX1BJ9Z

President Barack Obama bends over so that the son of a White House staff member can pat his head during a family visit to the Oval Office in this handout photo taken in Washington May 8, 2009 and later released by the White House. REUTERS/Pete Souza/The White House/Handout

Cleopatra Pendleton, mother of slain honor student Hadiya Pendleton, meets U.S. President Barack Obama after Obama spoke about measures to combat gun violence during a visit to Hyde Park Academy in Chicago, Illinois February 15, 2013. Pendleton was in the Presidential box during the State of the Union three days ago in Washington. REUTERS/Kevin Lamarque

U.S. President Barack Obama (L) and his wife Michelle (R) paint quotations attributed to slain civil rights leader Martin Luther King Jr during a day of service in King's honor at the Browne Education Campus school in Washington, January 16, 2012. The quotations read: "The time is always right to do what is right" and "I have a dream". REUTERS/Jonathan Ernst

A man in a suit and woman with children walk past a pile of protest signs along Flatbush Avenue as protesters demonstrate for higher wages in the Brooklyn borough of New York City April 15, 2015. U.S. fast food workers fighting for better wages enlisted students, healthcare workers and racial justice activists to swell the ranks of rallies set for Wednesday in 230 cities. REUTERS/Lucas Jackson - RTR4XFNP

A file photo of jobseekers standing in line to attend the Dr. Martin Luther King Jr. career fair held by the New York State department of Labor in New York April 12, 2012. REUTERS/Lucas Jackson

U.S. President Barack Obama waits to deliver the commencement address to the 2016 graduating class of Howard University in Washington, U.S., May 7, 2016. REUTERS/Joshua Roberts - RTX2D9RY

A member of the crowd wears a t-shirt with an image of President Barack Obama during a rally led by Tracy Martin, father of Trayvon Martin, in Miami, Florida July 20, 2013. Trayvon Martin's parents were due to lead demonstrations in New York and Miami on Saturday, as protesters across the country rallied to express anger over the acquittal of George Zimmerman, the man who shot and killed the unarmed black teenager. REUTERS/Andrew Innerarity

A supporter listens to U.S. President Barack Obama speak at a campaign rally for Democratic Senator Barbara Boxer at University of Southern California in Los Angeles October 22, 2010. Obama is on a four-day, five-state swing to support Democrats in the upcoming election. REUTERS/Kevin Lamarque

U.S. President Barack Obama (3rd L) participates in a march across the Edmund Pettus Bridge in Selma, Alabama, March 7, 2015. Also pictured are first lady Michelle Obama (L), U.S. Representative John Lewis (D-GA) (2nd L), former first lady Laura Bush (2nd R) and former president George W. Bush (R). The event comes on the 50th anniversary of the 'Bloody Sunday' march at the bridge, where police and state troopers beat and used tear gas against peaceful marchers who were advocating against racial discrimination at the voting booth. REUTERS/Jonathan Ernst

U.S. President Barack Obama meets with President-elect Donald Trump in the Oval Office of the White House in Washington November 10, 2016. REUTERS/Kevin Lamarque TPX IMAGES OF THE DAY - RTX2T2GN

U.S. President Barack Obama's birth certificate that was released by the White House in Washington April 27, 2011. The White House on Wednesday released a longer version of President Barack Obama's U.S. birth certificate to try to quiet a debate within Republican circles that he was not born in the United States. REUTERS/The White House/Handout

Photographed through a prison cell window, U.S. President Barack Obama tours the El Reno Federal Correctional Institution in El Reno, Oklahoma July 16, 2015. Obama is the first sitting president to visit a federal prison. REUTERS/Kevin Lamarque - RTX1KKUD

Image used for illustrative purpose. Michael Norton, 23, who does not have health insurance, stands with his cat M.J. at a Covered California event which marks the opening of the state's Affordable Healthcare Act, commonly known as Obamacare, health insurance marketplace in Los Angeles, California, October 1, 2013. Technical glitches and heavy internet traffic slowed Tuesday's launch of new online insurance exchanges at the heart of President Barack Obama's healthcare reform, showcasing the challenge of covering millions of uninsured Americans. REUTERS/Lucy Nicholson

U.S. President Barack Obama meets members of the audience, including Cameron Sterling (R), son of Alton Sterling who was shot and killed by white police officers in Baton Rouge, after taking part in a televised town hall about trust and safety in our communities in Washington July 14, 2016.REUTERS/Kevin Lamarque - RTSHZ1G