Political coverage is often compared to a horse race, but football — America’s primary pastime — provides the more apt analogy. Both are ground-acquisition games, take a long time to play and feature almost as much advertising as action.

Think Bush vs. Gore in 2000, which was not only a nail-biter, but went into overtime!

What happens, though, when the game starts slipping away and the outcome appears fairly certain, especially in this age of perpetual campaigns, with cable-news networks locked in ideological combat? For that part of the media addicted to the adrenaline rush of politics, it’s difficult to pull back on the throttle, much less change direction.

In this regard, the media approach to politics parallels sports in several key ways.

Listening to Al Michaels call a football game is comforting, mostly because he doesn’t oversell it. Yes, he tries to make the action exciting, but if the score is lopsided, he turns to other topics.

An old pro like Michaels increasingly represents a counterpoint (and for many a tonic) to a newer breed of announcers, who feel compelled to call every moment as if on verbal steroids. In their golden throats, a 45-10 third-quarter blowout still sounds like the Super Bowl.

There are two months left before the 2012 U.S. election, and to borrow sports cliches, the sides are evenly matched, and there’s no telling what can happen on any given (in this case) Tuesday.

Yet like those aforementioned sports announcers, the networks breathlessly chronicling the campaign’s every twist have a vested interest in ensuring the audience stays engaged, right until the end.

Unfortunately, there’s little sense hard-core conservatives and liberals are even watching the same content, or braced for disappointing outcomes.

Conservative icon Rush Limbaugh, for example, has dismissed recent polls showing President Obama moving further ahead, painting them as an attempt to depress the GOP base. He has even spoken about Republican Mitt Romney potentially winning in a “landslide.”

Those following the data — such as Nate Silver’s fivethirtyeight.com, whose forecasting was remarkably accurate in 2008 — know that while the national popular vote remains extremely close, the electoral-college math is becoming much more challenging to the Republicans. With huge states like California and New York firmly in the Democratic column, Romney needs numerous things to break his way in order to win. (At presstime, Silver put the likelihood of Obama winning, vs. Romney’s percentage, at nearly 4-1.)

Are people on the fringes — particularly those whose media diet seldom includes venturing beyond comfortable echo chambers — aware of such formulations? And do the media egging on supporters, right or left, really have any incentive to give their audience the full story — or permission to stop hanging on the campaign’s every nuance?

Of course, the most obvious conspiracy theory media-wise would be that conservatives are secretly rooting for Obama, while liberals pray (well, sort of) for Romney.

Because while some commentators see Obama as a socialist intent on bringing America to ruin, there’s no arguing one point: As Fox News and Limbaugh have discovered, being the media voice of the opposition is good for business.