The momentum in the 2004 presidential race has shifted back and forth over the past few months. But the polls have consistently shown a dead heat. Right now, on day three of the Republican convention, the momentum appears to be favoring President Bush. But as the Republicans celebrate first lady Laura Bush's success at the convention Tuesday night and prepare for Vice President Cheney's appearance, the Democrats came out swinging with new ads and a forceful speech by Kerry. Hear NPR's Mara Liasson and NPR's Melissa Block.