"The presidential campaigns and their allies are zeroing in mainly on nine swing states, bombarding them with commercials in the earliest concentration of advertising in modern politics," the New York Times reports. "With so many resources focused on persuading an ever-shrinking pool of swing voters like those here in Nevada, the 2012 election is likely to go down in history as the one in which the most money was spent reaching the fewest people."The battleground: Colorado, Florida, Iowa, North Carolina, New Hampshire, Nevada, Ohio, Pennsylvania and Virginia.