How does a war chest counterbalance apathy, unless you are talking straight cash payments? Obama got his 2008 turnout because of 2 things: (1) hatred of Bush; and (2) novelty. Neither of those things will be present in 2012. Regardless of the level of campaign funding, I just don't see how he gets Joe the parking attendant, who never voted prior to 2008 and voted in 2008 because it was the cool thing to do that he thought would change the world, to turn out again after seeing that it didn't change shit from his perspective. He'll be at work or playing XBox or in the drive-thru line at Wendy's, just like any other Tuesday.
Because I find your encapsulation of the 2008 turnout to be pretty naive (I doubt you really mean it), and your prediction on 2012 to be largely hope-based.
In 2008, Obama put more boots on the ground going door-to-door, more effort into voter-by-voter registration, more cash into database construction and updates, more workers into the field drumming up Dems for a quick jaunt down to the polls on election day, and more money on the airwaves than any candidate before him. Ever. You think this wasn't fundamentally important to high turnout?
In politics money talks, not hatred, "hope and change," or novelty. There is a direct, quantifiable correlation between dollars legally spent in any district and turnout. You might not always be able to spend enough to sway voters -- although you usually can -- but you can
always spend enough to drive turnout. In 2008, Obama sent workers to stop by and speak to basically every registered Democrat in any metropolitan area. It was incredible.
He can do it again in 2012, because he can make up for lost volunteers with paid employees. This time around, he'll have more even money to get people to vote. There are always more Dems than Pubs, X-Box playing Wendy's eaters notwithstanding. And Obama's reelection does not hang in the balance of the whims of some skateboarder who just turned 22. Obama just needs a decent turnout to win--he doesn't need 2008 numbers to stave off a fairly historically weak GOP field while already holding the office.
And the idea that Dems are suddenly going to be passive and not care who wins is silly, even if they didn't get everything they wanted in the first term. The left has a pretty healthy dislike for the right that will get them to bother to vote. Further, getting voters to their first election is usually the challenge. Getting them to their second is much easier. With the improvement of voting technology and the advent of online outreach, this will likely be more and more true as we moving deeper into the internet era.
In 2008 Obama did harness a ton of enthusiasm, sure, and Bush hate, but he also had the cash to outspend McCain on logisitics something like 25:1, while being more organized and up-to-date on the best way to do it. The GOP will face similar margins in 2012. It's a mountain to climb.
Just my opinion.