Karl Rove's signature contribution to campaign politics was the insight that the most effective way to defeat an opponent was not to attack his greatest weakness, but to attack his greatest strength. (There's some vivid detail from Joshua Green's classic 2004 article on Rove's history as a campaigner. Sample: Your client's opponent volunteers to help abused children? Spread rumors that he's a pedophile!) There's no doubt that at the moment, Mitt Romney's greatest strength is the idea that as a successful businessman, he will do a good job stewarding the American economy. In fact, that may be his only strength. He's stiff and awkward, he has a well-earned reputation for changing his stated beliefs to suit the political moment, he just went through a primary campaign in which he took numerous unpopular positions in order to please an extremist party base, the severe unpopularity of his party in Congress will drag him down, he has nothing particularly compelling to say about foreign policy—you get the picture.
For a while, Democrats believed that if the economy kept improving, that would leave Romney with no rationale for his candidacy. But at the moment, the economy looks like it will continue to shamble forward, moving in the right direction but not with enough momentum to make everyone feel things are going really well (though there will be six more monthly job numbers released between now and election day, and anything could happen). That means that it will be necessary for the Obama campaign to go after Romney on the economy. As Mark Halperin of Time reports, the Obama campaign's "research suggests Romney has exactly one rhetorical path to victory, as a can-do businessman able to fix what’s broken. Chicago intends to focus as much of its formidable firepower as necessary to dismantle Romney on that front."
What I'd really like to see is the Obama campaign taking on the whole idea that because you made a lot of money in business, that means you'll be brilliant at setting macroeconomic policy for the country. This idea gets repeated a zillion times every election by candidates saying, "I'm not a politician, I'm a businessman," as though that were a compelling argument for why you'd be successful in politics, not business. This is a pet peeve of mine I've written plenty about; see this article for a rundown of all the reasons it's absurd. But I'm not naive enough to think the Obama campaign is going to spend time arguing against something so many people believe in without thinking. Instead, they're going to comb through Romney's career and figure out what combination of attacks will create a negative association in the public's mind when the words "Romney" and "business" are mentioned together. Maybe the key will be his personal wealth and hilarious habit of saying things that reinforce his distance from the struggles of ordinary people, or maybe it will be stories of layoffs at companies Bain Capital acquired, or maybe it will be some new story we haven't yet heard of. But they'll be attacking him on it, good and hard.
In response, Romney will keep saying, "I know how the economy works," which is just an assertion, not an argument. For the moment, that seems to be somewhat persuasive; polls show him leading on the question of who would do a better job managing the economy (see here or here).
Romney does have a lengthy economic plan, but it amounts to the same thing Republicans always advocate: tax cuts, particularly on the wealthy; spending cuts in domestic programs; eliminating regulations; free trade; undermining labor unions, and so on. The closest thing to an innovative idea is the creation of a "Reagan Economic Zone," which presumably will create wealth through the repeated incantation of the great one's name.
Which is just the point: if Mitt Romney's experience in private equity gives him such unique understanding of the economy, why is what he proposes exactly what you'd hear from any Republican who spent his working life in government? It's partly because Romney is a Republican, and things like tax cuts and reductions in regulation are just what Republicans believe. But maybe it's also because when it comes to the things government can do to affect the economy, being a businessman doesn't give you such special insight after all.