Hillary Clinton invoked Harriet Tubman at a mega-fund-raiser last night, telling young supporters she'd fight to "take back the White House" just as the escaped slave fought to free others. The Democratic presidential hopeful brought out the whole family for the "low-dollar" event at the West Side's Pier 94. But Bill Clinton and their daughter, Chelsea, left the limelight to the candidate, who found herself struggling with a faulty microphone. "This reminds me of one of my favorite American heroines, Harriet Tubman," the senator told 1,800 cheering supporters when her mike was restored. "She made it to freedom after having...