NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Vermont Sen. Bernie Sanders appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, and Vermont Sen. Bernie Sanders appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Maryland Governor Martin O’Malley appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Maryland Governor Martin O’Malley appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Secretary of State Hillary Clinton and Vermont Sen. Bernie Sanders appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Secretary of State Hillary Clinton appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Maryland Governor Martin O’Malley appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Secretary of State Hillary Clinton and Vermont Sen. Bernie Sanders appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Maryland Governor Martin O’Malley appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, and Vermont Sen. Bernie Sanders appear during the “NBC News – YouTube Democratic Canfidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, Vermont Sen. Bernie Sanders, Lester Holt and Andrea Mitchell appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Maryland Governor Martin O’Malley appears during the “NBC News – YouTube Democratic Canditates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Secretary of State Hillary Clinton and Vermont Sen. Bernie Sanders appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Secretary of State Hillary Clinton appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Maryland Governor Martin O’Malley appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Vermont Sen. Bernie Sanders appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, Vermont Sen. Bernie Sanders, Lester Holt, and Andrea Mitchell appear during the “NBC News – YouTube Democratic Candidates  Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, and Vermont Sen. Bernie Sanders appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Secretary of State Hillary Clinton appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Secretary of State Hillary Clinton appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Andrea Mitchell and Lester Holt appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Vermont Sen. Bernie Sanders appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Maryland Governor Martin O’Malley appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, Vermont Sen. Bernie Sanders, Lester Holt, and Andrea Mitchell appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Andrea Mitchell and Lester Holt appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, Vermont Sen. Bernie Sanders, Lester Holt, and Andrea Mitchell appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, and Vermont Sen. Bernie Sanders appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Fmr. Maryland Governor Martin O’Malley appears during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, and Vermont Sen. Bernie Sanders appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Kate Snow and Chuck Todd appear before the “NBC News – YouTube Democratic Candidates Debate on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: Kate Snow appears before the “NBC News – YouTube Democratic Candidates Debate on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)

NBC NEWS – ELECTION COVERAGE — NBC News – YouTube Democratic Candidates Debate — Pictured: (l-r) Fmr. Maryland Governor Martin O’Malley, Fmr. Secretary of State Hillary Clinton, and Vermont Sen. Bernie Sanders appear during the “NBC News – YouTube Democratic Candidates Debate” on Sunday, January 17, 2016 at the Gaillard Center Theatre in Charleston, SC — (Photo by: Virginia Sherwood/NBC)