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Poor Glenn Beck. He's been freaking out all week over today's One Nation rally on the National Mall in Washington. You can tell that he's a little worried that the massive turnout is going to make his little Beckapalooza gathering in August maybe look not quite so big as he wants everyone to believe it was.

Which is why, on his radio show Thursday, he was busy smearing groups like National Council of La Raza as a "nasty, take America and give it to the Mexicans" group, and predicting that today's marchers would be violent. Right.

Of course, as Greg Sargent explains, the turnout has significance well beyond simply Glenn Beck's ego:

So how many people will turn out at tomorrow's big lefty rally on the national Mall? It's an important question, because the rally is turning into a key test of whether Dems can close the much-ballyhooed enthusiasm gap.

The Service Employees International Union is expecting some 75,000 of its members to turn out tomorrow, SEIU spokesman Teddy Davis tells me, an estimate based on the number of pledges to attend and the number of buses they've chartered. Members are coming from 22 different states.

Meanwile, AFL-CIO president Richard Trumka is vowing that labor will turn out a total of at least 100,000 at the rally, which is being dubbed "One Nation Working Together." There are multiple other groups involved in the rally, and they could add tens of thousands more people, though organizers expect labor unions to be the main turnout engine tomorrow.

It's unclear whether these numbers will prove accurate. But if turnout is healthy, it's going to be very interesting to watch how this rally is received. The dominant narrative about this fall's elections, of course, is that Dems are in for a shellacking because they are not going to be able to recapture the enthusiasm and turnout of 2008 and because the left has failed to match the oppositional energy of the Tea Party.

Comparisons to the Beck rally are an important part of this picture, of course, since Beck claimed -- without a whit of credible evidence -- that there were half a million people at the Beckapalooza wankfest. After all, any real comparisons of the Beck crowd with last spring's March for America -- where the crowd was estimated at between 100,000 and 200,000 strong -- would reveal that it wasn't even the largest crowd to march on the Mall this year.

And yet the coverage of the spring immigration march was nearly nonexistent when it came to the national media -- particularly Fox News -- who instead that weekend focused their coverage on a relatively tiny handful of Tea Partiers who were up on the Hill desperately (and futilely) protesting the imminent passage of health-care-reform legislation in the House.

Indeed, the media have devoted huge amounts of coverage to the relatively smaller Tea Party protests all this past year. Likewise, there has been almost no coverage -- outside of Beck's fulminations -- of today's march by those same media.

As Sargent says:

Granted, it's hard to compete as spectacle with those lurid signs and outsized three-corner hats, but given how ubiquitous and heavily promoted the "enthusiasm gap" narrative has been, you'd think a healthy turnout tomorrow would be considered somewhat newsworthy.

Yeah, you'd think. But then, in the current media environment, newsworthiness has become a function of the effectiveness of right-wing propaganda.

I'll be there covering the march this morning, which begins at 11 a.m. EDT. Video will be forthcoming -- including some shots giving you an idea of the crowd's size.