Walter Shapiro, the political-coiu-mnist for USA Today and a seasoned presidential campaign reporter, decided that for the 2004 Democratic race,the most dramatically unpredictable nomination fightin three decades, he would get to the candidates early,when their campaign stops were small gatherings in New Hampshire living rooms and Iowa union halls, their staffs a beleaguered aide or two, their ideas not yet codified in sound bites. He hoped to capture the drama and the behind-the-scenes stories of the opening days of a presidential race, the uncharted "Invisible Primary," when the candidates are open and accessible, and poli- tics is still truly fun.