Doug Liman’s new film, “Fair Game” continues the Cannes Film Festival‘s trend of politically-themed movies this year. Naomi Watts plays Valerie Plame and Sean Penn plays her husband, Joe Wilson, as they become entangled in the infamous lead-up to the Iraq War. Former ambassador Joe Wilson debunked a report that Iraq had purchased “yellowcake” uranium from Niger, thereby incurring the wrath of Dick Cheney’s office. In retaliation, the administration exposed his wife, Valerie Plame, as a CIA operative which effectively ended her career.

The most compelling parts of the film deal with the political pressure put upon the CIA to find that Saddam Hussein had WMD. One of the more chilling exchanges occurs when Scooter Libby bullies an analyst into backing down from his own conclusions. Helpful Iraqis were cruelly betrayed; the film hints that the leak of Plame’s identity may have killed some of her sources.

Unfortunately, the director gives at least equal emphasis to how the leak affected the Wilson household. As the film veers into “marital crisis” territory, it loses gravitas.

The casting was another unfortunate decision. Valerie Plame is clearly a complex, fascinating woman but Naomi Watts is simply too lightweight to plumb her depths. For an actress, it’s the role of a lifetime, but Watts doesn’t come up with the goods. Sean Penn also struggled to convey his character’s mixture of bluster and idealism. His performance was passionate but actorly.

Still, the film is worth seeing if only as a reminder of a shameful episode in American history.