WASHINGTON—For 18 months, it has gone on and on and on. Now the battle for the White House is shrinking to a pinhead — just 180 minutes is all.

Such are the spiralling stakes of the two final presidential debates: 90 minutes on Tuesday in Hempstead, N.Y., where CNN’s Candy Crowley will oversee a town-hall style showdown, and another 90 next Monday in Boca Raton, Fla., with CBS’s Bob Schieffer grilling Barack Obama and Mitt Romney on world affairs.

Eighteen months versus 180 minutes. The difference rings hollow, if not absurd. What, really, is the point of so epic a campaign when the tipping point itself lasts no longer than an average college exam?

And what does it say about America’s political attention span?

READ MORE: U.S. election coverage

Not anything good, according to media analyst Jack Lessenberry, who tracks election coverage at Michigan’s Wayne State University school of journalism.

Lessenberry likens the shrinking retentiveness of the average American voter to that of “a six-week old puppy.”

And the debates, now more than ever, are the puppy chow — drama-coated kernels of confrontation in place of the far less palatable complexities of policy wonkdom.

It’s a perfect fit for the emerging digital mediascape, which lives or dies by its ability to shape the story into bite-size format. Not so perfect, says Lessenberry, for voters who should be basing their decisions on more than a single night’s worth of news.

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“People talk about a media conspiracy. But what’s really happening in this election is an accidental conspiracy — (the media) want this to be a three-act play,” he told the Star. “Because the alternative is a race where nothing change, which would be tremendously boring for cable news.

“The opening act was all those months with Romney characterized as a cold, uncaring rich man who keeps falling over himself, unable to ride the bicycle.

Act 2 was Romney picking himself up and knocking Obama for a loop (in the first debate).

The final act, said Lessenberry, hinges on the 180 minutes. “It will either be Obama coming back and ‘The Champ Wins Again’ or the opposite, ‘Romney Defies the Odds, Goes All The Way.’ ”

The sheer decibel level of the postdebate echo chamber — driven now as much by social media as by traditional media outlets — is not only deafening; it can also drown out yesterday’s news like never before. A new Etch-a-Sketch with every meal.

“If you listened to the echo chamber, that first debate was supposedly as bad for Obama as Stalingrad was for the Nazis,” said Lessenberry.

“Yet if you go through the transcript, there were no big gotcha lines that made the debates of previous years so memorable.

“It suits the dramatic needs of news television to build up that tension. And now the comeback angle is hovering ahead of us, waiting for a tougher Obama to fit into the narrative.”

The average sound bite on American television, meanwhile, has fallen from 43 seconds in 1968 to seven seconds today. “Jesus wouldn’t get 43 seconds if he came back today,” said Lessenberry. “And it’s just plain whack to expect anyone to say something profound about the world economy in that amount of time.”

One of the predictable go-to devices for debate coverage is “Five Things” packaging — “Five Things Obama Will Say Tonight,” “Five Takeaways from the Showdown in Denver.”

Lessenberry suggests that “Five Things to Help You Forget Yesterday’s Five Things” might be more accurate.

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“We’re all coming to understand that the faster the news moves, the faster yesterday is forgotten. Many people thought the image of Mitt Romney as a cold, uncaring figure was pretty much set by the ‘47 per cent video.’ But it’s largely been forgotten.

“That’s astonishing, really. A month ago everyone was talking about the dazzling performance of Bill Clinton at the Democratic convention. Does anyone even remember that now?

“There once was a shelf life to the narrative in American politics. I’m not sure it even exists anymore.”

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