At a time when political documentaries have become all the rage, Robert Greenwald is emerging as the form's Joyce Carol Oates, pumping out film after film about timely controversies, from the 2000 election ("Unprecedented") to Fox News Channel ("Outfoxed"), and from the Bush administration's run-up to the war in Iraq ("Uncovered: The War on Iraq," opening today) to the implications for civil liberties of the Patriot Act (the upcoming "Unconstitutional").

Greenwald's films don't break any formal ground -- they're prose, not poetry, hewing to a conventional clips-and-talking-heads format. But they are quick, efficient polemic, the cinematic equivalent of a good op-ed piece. In "Uncovered" -- a shorter version of which was shown last year in a series of house parties sponsored by the anti-Bush organizations MoveOn.org and the Center for American Progress -- Greenwald marshals dozens of impeccably credentialed witnesses to debunk the case made for going to war. We hear from former CIA, State Department, Pentagon and military officials whose arguments have been given added steam recently by major news institutions, this one among them, admitting that their prewar coverage was insufficiently skeptical. Whether "Uncovered" will change any minds -- whether, as Greenwald obviously desires, it will contribute to voting George W. Bush out of office in November -- is less than clear in a season when political energy seems increasingly to be directed at showing up at the multiplex, if not the polls.

Still, even for the already-convinced who will most likely form its biggest audience, "Uncovered" provides convincing and well-organized ammo for their case. Viewers will be familiar with many of the talkers, including former weapons inspectors Scott Ritter and David Kay, former ambassador Joseph Wilson, former Army Gen. Patrick Lang and former Nixon administration official John Dean. Systematically breaking down the administration's arguments regarding WMD and terrorism, as well as the use of dubious informants, manipulated intelligence, intimidation and a supine media and Congress, they provide quietly persuasive arguments against having invaded Iraq. Perhaps even more damning are the guys we've never seen on TV -- the career intelligence operatives and diplomats -- who quietly deconstruct what they see as the political theater that President Bush, Vice President Cheney, Secretary of State Colin Powell and national security adviser Condoleezza Rice engaged in to sell the war to the American people.

It's smart, engaging discourse, not just about the war in Iraq but about the tactics and style of the Bush administration and the Bush doctrine, which accepts the idea of preemptive war. "Uncovered" is important for everyone, not just anti-Bush partisans, to see: It lays out with more light than heat one side of a debate in which everyone should be passionately engaged.

Uncovered: The War on Iraq (56 minutes, at the Avalon) is not rated.

"Uncovered" recounts Secretary of State Colin Powell's presentation to the Security Council, then undercuts him with highly credible interviews.