"America's Got Talent" (9 p.m., NBC): OK, America, it's time for you to decide who stays and who goes. The quarterfinals begin tonight as 12 of the Top 48 acts perform at Radio City Music Hall and the vote is turned over to the viewers.
"Losing Iraq" (10 p.m., PBS): This 90-minute edition of "Frontline" takes a big-picture, in-depth look at the war we left behind and the crisis that has erupted since. What went wrong? How did we get here? And what happens now?
"Dark Horse Nation" (10 p.m., History Channel): Pour yourself a cold one. This new reality series follows the day-to-day adventures of the Dark Horse Brewing Company, where they combine great craft beer with innovation and a renegade approach to business.
Also on Tuesday: