Join us [online Thursday afternoon](http://www.pbs.org/newshour/) for a robust livestream and live blog, for the 6 p.m. NewsHour and on air at 9 p.m. for the PBS debate special with co-anchors Gwen Ifill and Judy Woodruff and analysis from Mark Shields…

People take in a preview of "Roy Lichtenstein: A Retrospective" at the National Gallery of Art in Washington, D.C. The exhibition of the U.S. pop artist's work runs Sunday through Jan. 13, 2013.