The former Massachusetts governor announced his candidacy today in neighboring New Hampshire, arguing that “Barack Obama has failed America.”

Two months earlier, Romney said that Obama and his economic team “just don’t know how jobs are created in the private sector,” before contrasting it with his own experience as co-founder of private equity firm Bain Capital: “Sometimes I was successful and helped create jobs, other times I was not.”

That last line reflects a very narrow line Romney will need to walk: Emphasizing his past business experience to convince voters that he would be a competent economic steward, while simultaneously not getting tripped up by past investments gone bad. For example, his 1994 Senate bid against Ted Kennedy was partially derailed by video ads of striking workers at a Bain Capital portfolio company called Ampad.

But don’t expect Romney to perform this balancing act too much over the next several months. Not because he isn’t prepared to do so, but because he’s unlikely to be forced into it by his Republican rivals.

Today’s Mitt Romney has the exact same business experience as 2008 Mitt Romney, and that guy was almost never challenged on Bain-related issues.

I’ve gone back to old newspaper stories, and have been unable to find an example of McCain or any other candidate discussing Ampad, Bain-related layoffs or private equity in general. In fact, the only real exception was when Mike Huckabee floated a conspiracy theory about how Bain’s investment in Clear Channel — made long after Romney left the firm — was a possible explanation for Huckabee’s failure to secure endorsements from some of Clear Channel’s conservative talk radio hosts.

Maybe it’s just a GOP thing: Don’t bust on private sector business experience, because we believe the private sector is always superior to the public sector. And perhaps this season’s Tea Party influence will alter things a bit, since Romney may seem a bit too chummy with Wall Street (although that likely will be overlooked in favor of haranguing Romney over the Massachusetts healthcare insurance mandate).

If Romney does manage to win the nomination, then he’ll have to climb onto the tight rope. In fact, I wouldn’t be surprised if some Obama operative is already scouring Indiana, trying to connect with of those old Ampad employees. But that’s Romney’s problem — and private equity’s problem — for another day. For now, he simply gets to focus on his fonder memories.