BOSTON — When Barack Obama was delivering the finest keynote address heard at a Democratic National Convention since Mario Cuomo’s 1984 speech in San Francisco, the nation’s broadcast television networks were airing their usual mix of police dramas, a program about a Disney cruise and a show that asked the question: “Who says pageant girls don’t eat?’

ABC, NBC and CBS chose not to air any of Tuesday night’s convention proceedings. For the first time since the development of broadcast television, Americans could not tune into one of their local commercial television stations and watch nation’s oldest political party reinventing itself for the newest campaign.

To be sure, the cable networks offered a reasonable mix of live convention coverage — ranging from the incessant play-by-play chatter of CNN to the potshots from Fox and the uninterrupted feed of CSpan — but the broadcast networks chose not to be carry the convention. As such, they sent a powerful signal regarding the extent to which they take seriously their responsibility to provide citizens with the information that is the lifeblood of democracy.

It is true that much of what is said from the convention podium these days adds up to little more than a partisan informercial. But there are still meaningful moments, and Obama’s address was one of them. In fact, the Illinois state senator’s speech was an exceptionally significant expression of the ever-evolving story of American citizenship and political engagement. Obama’s often poetic message — with its “E pluribus unum. Out of many one” theme — was the talk of the convention.

It was not, however, the talk of the nation because, of course, the networks chose not give it the same time and attention they devoted to that program about the eating habits of their “pageant girls.”

The failure to broadcast the speech by a man many believe could be the country’s first African-American president struck even some media veterans as troubling. On ABC’s “The View,” co-host Meredith Vieira spoke of how, “After (Obama) got done speaking, I had chills” and complained about the decision of the networks to neglect the keynote address. “He is a man that America needed to see,” she said.

By any measure, Vieira is right.

But don’t expect broadcast television to get the message. The networks have replaced the civil and democratic values that once a played a role in decisions about what to cover with commercial and entertainment values that dictate a denial of seriousness or perspective when it comes to political stories.

That’s one of the reasons why so many Americans objected last year to Federal Communications Commission proposals that would have lifted the cap on the number of local TV stations a corporation could own — and the amount of the viewing audience network-owned stations could reach.

Despite the intensity of the FCC rule fight, the campaign for media reform in America is only beginning to have a serious impact on the political process. But it is growing. And, while the neglect by the networks of the Obama speech is troubling sign, there is an encouraging sign coming out of this convention.

On Tuesday night, delegates approved a platform that recognizes the burgeoning media reform movement in the United States. The language that was added to the platform, under pressure from unions such as the Communication Workers of America that have become increasing active in the fight for media reform, was not radical. But it was on message. “Because our democracy thrives on public access to diverse sources of information from multiple sources, we support measures to ensure diversity, competition, and localism in media ownership,” argues the new platform language.

There’s a lot more that Democrats should stand for with regard to media reform. And, hopefully, anger over the decision of the networks to skip coverage of Tuesday night’s proceedings will cause party activists to recognize that complaining about the conservative bias of Fox is not enough. When the major networks choose pageant girls over political history, they themselves are making the case that democratic renewal cannot be achieved without radically altering the style and structure of our media system.