Heard about the big D.C. rally Saturday? Probably not.

It's bad enough when you throw a party and nobody comes. Well, what if you hold a rally, plenty of people come, but nobody – meaning, in this case, the national media – pays attention?

That scenario seems to be playing out right now as what is possibly the mother of this midterm election’s Washington rallies slips into town under what Harry Potter fans might call an invisibility cloak.

A group called One Nation Working Together, which bills itself as "a nationwide liberal organization dedicated to networking progressives together for true hope and change," has been planning its big event for Oct. 2 since May. It has some 500 national organizations on its affiliated roster and has buses and caravans of folks from all over the country set to arrive for the noontime, four-hour rally – not to mention sister events in eight cities and dozens of house parties.

Yet, punch in "Washington rally" for a Google search and all you hear about is the upcoming Stephen Colbert/Jon Stewart event on Oct. 30 – or lingering deconstructions of the Aug. 28 Glenn Beck gathering on the steps of the Lincoln Memorial. A single-page, A13 mention in The New York Times and a smattering of other national press – mere days before the march – round out the underwhelming national media nod.

So what gives? Is this just a case of bad party-planning chops or something deeper?

For starters, points out Gordon Coonfield, associate professor of communications at Villanova University in Pennsylvania, the two, high-profile rallies had the benefit of supportive national media outlets to stoke interest. Fox News provided Glenn Beck with a national megaphone, while Comedy Central fans get a nightly stoking from both Jon Stewart and Stephen Colbert’s shows.

It’s a shame, he says, “when the good, old-fashioned community and grassroots organizing behind an event like the Oct. 2 rally takes a back seat to such personality-driven media events.”

But the wan national profile of Saturday’s event also speaks to differences between liberal and conservatives, says longtime political observer Jim Goyjer, vice president of the public relations firm Carl Terzian Associates.

“The problem with the Democrats and with the progressives is that they are never on the same page,” he says.

He says that he has been listening to progressive radio talk-show host Thom Hartmann talk about an event he’s covering in Washington this weekend without hearing any mention of the larger, One Nation movement.

“There have been several books written why the Republicans are always on message and the Democrats are hardly ever on message, and this rally is another example,” Mr. Goyjer says. Noting that the message of the march is to promote diversity and inclusion of many points of view – in a civil, non-sensational gathering – this very inclusivness will push it off the national media radar.

“Civilized rallies are not covered because they are not visually exciting for TV,” he adds.

Nonetheless, the team behind the rally says it is Facebooking, Twittering, texting and emailing its way to an impressive turnout come Saturday. Noting that major national media outlets such as NBC, CNN and yes, Fox News, have applied for media credentials, One Nation communications director Denise Gray-Felder says she is confident that the event will garner the attention it deserves when the weekend arrives.

Her New York colleague, Cheryl McCants, says that although the event has yet to finalize a list of speakers for the afternoon, “we have the most important voice of all, the voice of the people.”

Benjamin Todd Jealous, chief executive of NAACP, is one of the rally’s prime organizers. “We are living through a very particular moment in American history," he says via e-mail. "It is one in which diversity is increasing, while prosperity is decreasing. Barring great social movement, this is a formula for a battleground.”

Mr. Jealous says he sees the group's breadth and diversity as its signal strength and emphasizes that the rally is part of a movement to bring people together to solve pressing, national problems.

Some conservative bloggers have picked up the trail. Daniel Foster at National Review slams the event for what he regards as its extreme left leanings, noting that while the rally will consist of the NAACP, the AFL-CIO, National Gay and Lesbian Task Force, National Council of La Raza, and other liberal groups, it will also embrace: Communist Party USA, International Socialist Organization, Planned Parenthood, Democratic Socialists of America, and Code Pink.

But as the election season swells with an increasing number of events, New York political analyst Jerry Kremer, chairman of Empire Government Strategies, suggests this march may suffer from what he calls rally fatigue. A lack of a single, distinctive message emanating from the rally is not helping its profile in the national consciousness, he adds.

“There is just too much going on,” Mr. Kremer says, adding that these events tend to draw the faithful without sending out a clear effective message. If the public perceives that there are too many rallies, he adds, "most likely more groups will decide not to do them because they aren’t effective.”