Political consultants are finessing a kind of climate change on the current election season, flowing a tsunami of advertising cash into media much sooner—and with different buying strategies—than ever before.

Still, the average presidential candidate will only devote 1 percent of his or her ad budget to the Web, and lead candidates are likely to dedicate only about 5 percent.

The McCain campaign is already reaping the rewards of online advertising, getting a return of about $3-$4 in donations for every dollar they spend on search, according to Connell Donatelli's Eric Frenchman.