After President Obama proclaimed yesterday that he hadn’t grown up with a “silver spoon” in his mouth, Mitt Romney took great umbrage, declaring that he wouldn’t apologize for his father’s success. Indeed, the Post’s Amy Gardner reports that Romney is sensitive to claims that he grew up wealthy, and has even taken to asserting that he grew up middle class and only moved to a tony suburb in his teens, when his father took over American Motors.

But Alec MacGillis reads the leading book on Romney’s life story and finds that Romney is subtly revising his biography to downplay the advantages of his youth. MacGillis concludes:

Romney’s hardly the first candidate to try to talk down his roots. And yes, his outsized wealth is the direct result of his own hard work at Bain Capital. But it requires willful blindness to ignore the advantages that carried him through his first decades in life. And it’s the job of the rest of us to hold him to the basic facts of his biography, even as he now tries his best to blur them.

Yes, it’s important to hold Romney to the facts for their own sake. But there’s another layer to this that’s worth unpacking.

The upbringings of Obama and Romney — and the contrast between them — are relevant not just because presidential races are a clash of personalities and biographies. They also bear directly on the basic policy argument between the two men over how best to create opportunity and shared prosperity, a central dispute in this campaign.

Obama argues that government needs to play a larger role in facilitating opportunity, via more investments in education, financial aid, and so forth. He cites himself as an example of someone who might not have been able to advance in life without such assistance.

Romney, by contrast, argues that the government activism to combat inequality Obama advocates amounts to government-enforced “equal outcomes,” or worse, the politics of “envy” and “class warfare.” Romney insists that rolling back government and unshackling the private sector is the best way to combat inequality, by creating opportunity, shared prosperity and social mobility. Romney, too, has cited himself as proof of what the private sector can accomplish along these lines, if only we’ll let it. He has directly equated his own success with the benefits that “free enterprise” can shower on anyone.

In other words, both men are citing themselves as walking emblems of their own policy visions. No one is claiming that Romney didn’t earn his money or that he isn’t a very hard worker. But if Romney is going to argue that his own success proves that unshackling the free market is the primary way to facilitate broadly shared prosperity and opportunities for those who currently don’t share in either — and that Obama’s call for more government efforts to promote both would be counter-productive — the early advantages Romney enjoyed are directly relevant to the debate.

Even Romney’s own supporters will argue that his biography — his business success — is central to his overall case about the virtues of free market capitalism. There’s no reason, then, that his early years aren’t fair game for the discussion.

The contrast in the two men’s story arcs is central to this race, in more ways than one.