"All the King's Men" is an often fascinating look at the dark side of populism and the rise of a demagogue.

It's beautiful to look at and to listen to, capturing images of the American South that might have been plucked from a portfolio of WPA-sponsored photographs and employing language that verges on poetry.

It's well acted by Sean Penn and Jude Law.

The only problem is I didn't care.

For all the things it does right, Steven Zaillian's new screen adaptation of Robert Penn Warren's Pulitzer Prize- winning novel is a letdown where it really counts. It fails to deliver a gripping, emotional experience.

The rise of small-town activist Willie Stark (Penn) to the governorship of Louisiana — and the corruption he picks up along the way — is loosely based on the life of Huey Long, the Louisiana governor assassinated in 1935.

As in the book and 1949 film version, we witness Stark through the eyes of Jack Burden (Jude Law), a jaded newspaperman and son of Louisiana gentry who starts out championing Stark's attacks on the political establishment. Soon Jack finds himself co-opted, becoming one of Stark's closest advisers.

Initially Penn's Willie Stark is a rawboned bumpkin, earnest about reform and a painfully boring speaker. But when Stark realizes he's merely being used by the bosses to siphon votes away from another rural candidate, he's transformed into a fire-breathing, stage-stalking, fist-pounding political whirlwind.

He promises to pave rural roads, provide free books to school children, build public hospitals, tax the oil companies and throw the elitists out on their ears.

"There ain't nobody gonna help a hick but a hick hisself," Stark howls to roaring crowds of farmers in coveralls and housewives in faded print dresses.

Later scenes show Stark, now facing an impeachment vote, attending a nighttime rally like something out of Hitler's Germany. It helps that Zaillian filmed at the real Louisiana capitol, a phallic edifice that would have made Albert Speer proud.

This is great stuff. But Stark's transition from defender of the people to corrupt politico seems abrupt and arbitrary, and the film never explains why Jack continues to compromise himself by remaining in Stark's employ. Especially when Stark sends him to threaten Jack's godfather, a retired judge (Anthony Hopkins) who opposes the governor's thuggish methods.

Bottom line: "All the King's Men" starts out strong and then evaporates.