Both Air America Radio and the American Constitution Society should have been abject failures, and for the same reason. Each was an attempt to do for left/liberals what a similar entity---Rush Limbaugh and his clones in one instance; the Federalist Society in the other---had done for the right. Yet in both cases there was an important difference. Right-wing talk radio gave voice to a political constituency that was previously largely voiceless, just as the Federalist Society provided a haven for conservatives who felt outnumbered by liberal faculty and students at nearly all prestigious law schools, a place for them to meet, network, and plan their eventual ascension in a real world in which conservatives held considerable power. By contrast, before there was Air America Radio, there already were NPR for the latte liberal set, a network of African-American stations for the Democratic Party's most loyal constituency, and Spanish-language radio for the largest ethnic minority group in the country. About the only part of the Democratic base without an identifiable radio home was organized labor, and there was never anything in the format of Air America Radio that seemed designed to appeal specifically to union types. I'm not sure whom one would hire for UAW Radio, but Al Franken and Janeane Garofolo would not be at the top of the list. Likewise, the American Constitution Society entered what was already a crowded niche. Liberal law students did not feel marginalized and if they had a thirst for ideologically charged engagement, they had plenty of other options: they could become active (and many still do become active) in student branches of the ACLU, the Lawyers' Guild, and other organizations, or they could (and many still do) engage in activist lawyering through legal aid, clinics and externships.
How then to explain that while Air America Radio has been largely a flop, the ACS seems to have caught on? Air America Radio went bankrupt last year but has been kept afloat by an infusion of cash from real estate mogul Stephen Green and is in the process of re-launching under the leadership of his brother, perennial New York political candidate Mark Green. Whether it succeeds under the Greens remains to be seen. Meanwhile, the ACS website accurately describes itself as "a rapidly growing network" that is already "one of the nation's leading progressive legal organizations."
I don't have a perfect explanation for the different paths that Air America Radio and ACS have thus far taken. There is, to be sure, the obvious fact that despite the parallels I have identified here, the markets for talk radio and for law student/lawyer networks differ substantially. But there is another factor, I think, and it has to do with temperamental differences between liberals and conservatives, and between lawyers and others. Conservative talk-radio is an angry, strident medium, and, with important exceptions (including Al Franken himself), Air America Radio tried to emulate that style. That doesn't seem to work with most liberals, who generally prefer their political red meat laced with irony rather than vitriol. That's why the leading TV alternatives to Limbaugh, O'Reilly and Hannity are satirists like Stewart, Olbermann and Colbert. Indeed, Colbert is pretty obviously a direct parody of O'Reilly.
By contrast, the intellectual style of the Federalist Society has always been cordial, almost genteel. Thus, by adapting the means of the Federalist Society to liberal ends, ACS has adopted a style---that of the high-minded debating society---that liberals already find congenial.