With the average American spending more time online and on mobile devices like smartphones and tablets, the amount of time spent watching TV is leveling off and more of that viewing is time-shifted through DVRs. For advertisers across all industries, this means capturing eyeballs online and on mobile as well as through TV.

The New York Times recently highlighted the Romney campaign’s efforts to fight TV advertising’s “diminishing returns” and “get its ads in front of the increasing number of voters who are not watching traditional television.”

The lessons learned by the Romney campaign have consequences for all “down ballot” races as well. A recent SAY: media report [PDF] found that nearly a third of all likely voters aren’t watching “live TV.” The same study also notes that 88% of DVR owners are regularly skipping commercials on the TV content they do watch.

And it’s not just young people who are watching more video content with DVRs or via the Web. 15% of likely voters age 45 and older report watching less “live TV.” The same age group is using their DVR 12% more and watching video online 13% more over last year alone.

For campaigns, this means you can no longer rely on TV alone to reach voters with your message. Any TV buy must be complemented with a digital campaign reinforcing a similar message. This also means you have to think of online ads as more than just direct response campaigns.

In the new “two screen” advertising campaigns — where targeted audiences see messaging on both their mobile device and their TV — persuasion is the name of the game. As I’ve mentioned before, determining the overall goal for an advertising campaign is a critical first step in determining how you’ll measure success.

Persuading voters is all about capturing their attention in the right places and enough times to establish the message. This means your advertising has to follow the eyeballs and with less attention paid to TV advertising, online and mobile ads have to become part of your overall strategy.