Memo to President Barack Obama from your powerful friends in Hollywood: You are the president of the United States, clothed in immense power. Now use it. That, at least, seems to be the message of Lincoln, Steven Spielberg's surprisingly riveting examination of the 16th president's campaign to persuade that unruly collection of hicks, fanatics and thieves known as the House of Representatives to pass a Constitutional amendment abolishing slavery. Lincoln's Republican party outnumbered their Democratic rivals, but Constitutional Amendments require a two-thirds majority. So the challenge was to keep the Republican caucus in line and pick off about 20 votes from the other side. And so the arm-twisting began. If that sounds familiar, it should. It's reasonable to think that this film couldn't and wouldn't have been made at any other time.