After the 2000 presidential campaign, strategists for President Bush came to a startling realization: Democrats watch more television than Republicans. So by buying millions of dollars' worth of television advertising time, Republicans were spending their money on audiences that tended to vote Democratic. What to do? With the luxury of four years until the next election, the Bush team examined voters' television-viewing habits and cross-referenced them with surveys of voters' political and lifestyle preferences. This led to an unusual step for a presidential campaign: it cut the proportion of money that it put into broadcast television and diverted more to...