... Advertising Age named Barack Obama "Marketer of the Year" (in truth, they did that before the election, but still! I'll bet you're angling for person-of-the-year from Time, too. Leave some scraps for the rest of us, Prez!). My friends at ReachForce did a nice blog post about it, highlighting the key online marketing tactics.
But digging a little deeper, the folks at Wider Funnel
did a nice post about multivariate testing that barackobama.com was using, taking advantage of Google Website Optimizer. This type of granular, rapid-feedback testing is truly one of the differentiators of online marketing, with one caveat:
it requires statistical significance. If you don't have enough users to rapidly get answers, you risk making bad decisions. barackobama.com didn't have the problem.
An easy way to test is by just doing some ad-words campaigns with varied messaging, and then look at click-through rates... but make sure you are seeing enough traffic before you make any judgements. Even better is to keep tests going long-term, and (assuming you have closed-loop marketing of some kind) look at conversion rates of those leads. At a minimum, figure out where people are going after the initial click, so that you can make some assumptions about the quality of the visitors.