The reality of the 2012 campaign, however, is that both Obama and Romney — and nearly everyone else, for that matter — plunged in with apparent enthusiasm to the nonstop obsessions of cable and online media, with their focus on accusations, gaffes and sensational ideological and personal conflicts. While these factors were not new to 2012, they achieved a centrality to this race that they had never had before.

A summary of this election cycle’s media frenzies sounds like it could be put to music like Billy Joel’s “We Didn’t Start the Fire”: Michele Bachmann and the straw poll, Rick Perry’s “Oops,” “Nine, Nine, Nine,” Donald Trump, Herman Cain and harassment, “I like firing people,” “You didn’t build that,” “Put y’all back in chains,” “47 percent,” “Big Bird,” “binders full of women,” all the way to Election Day.

Sometimes Obama was the target of “cable chatter,” as when his clumsy wording (“You didn’t build that”) of an unremarkable assertion — that most successful business people benefited somewhere along the way from public education and vibrant communities — was pounced on by conservative commentators and Romney highlighted it for weeks. But his own team was equally relentless in exploiting marginal controversies to advantage, such as Romney’s awkward wording (“binders full of women”) about his genuinely strong record appointing women to senior positions in Massachusetts.

Across the ideological spectrum, politicians and operatives emphasize the way this media environment provides incentives for trivial arguments, and very often steep penalties for bold ideas or policy proposals.