YDE PARK ON Hudson" features former pot-smoking greenskeeper and ghostbuster Bill Murray as FDR, our Nazi-busting, Depression-ending president.

A comedian like Bill Murray as Franklin Delano Roosevelt?

You might as well cast Robin Williams as Theodore Roosevelt.

Oh wait. Robin Williams was Theodore Roosevelt. And he was pretty good too, albeit in the children's fantasy "Night at the Museum."

"Hyde Park" asks a little more of Murray, casting him as FDR on the eve of World War II, meeting in upstate New York with England's King George, cementing the special relationship that in the coming years would liberate Europe and defeat Adolph Hitler.

The stakes are high, but the mood in "Hyde Park" is light - director Roger Michell pitches the movie as a comedy, positioning FDR as the quietly offbeat head of a wacky household, which plays to Murray's strengths and gift for deadpan understatement.

Less funny is the movie's other plot thread, built around FDR's slow-burn seduction of his cousin, Margaret "Daisy" Suckley (Laura Linney).

Fifth cousin, but still.

Gross.

The movie is adapted from Daisy's letters and diary, and shows how FDR seduced the young-ish woman and added her to his sizable stable of ladies on standby to address his non-food appetites. A stable, as we see, that did not include his wife Eleanor (Olivia Williams with bridgework, hilarious).

As a comedy of clashing cultures and diplomacy - sophisticated British guests baffled by our informal and rustic ways, as the fate of the free world hangs in the balance - the movie works pretty well. Stuttering King George (Samuel West) gives a different spin on the same character of last year's "King's Speech," and especially so his wife (Olivia Colman), much more acidic than the Helena Bonham Carter version.

The movie stumbles, though, as it moves deeper into the nature and magnitude of FDR's unconventional sex life - you may never dislodge from your mind the scene of President Roosevelt being serviced in his car by Daisy as they listen to "Moonlight Serenade."

Michell flails for the right way to knit everything together. Daisy's naivete and ultimate seduction are played for laughs, and that makes her subsequent outrage (at finding out there is a veritable field of Daisys) seem out of place.

The movie never coheres, but will please fans of Murray. He doesn't transform himself into FDR, but he does transplant FDR into the pantheon of memorable Murray characters.

Blog: philly.com/KeepItReel