Franklin Delano Roosevelt used a wheelchair because of polio, but “Hyde Park on Hudson” paints a genial, warts-and-all portrait that demonstrates that he was in many ways a real live wire.

Charmingly represented by Bill Murray, the film’s Roosevelt is a jaunty bon vivant who enjoys his cigarettes, martinis, good conversation and plenty of extramarital sex. In an early scene he takes his distant spinster cousin Margaret “Daisy” Suckley (Laura Linney) for a spin in a custom-designed convertible. Driving it with hand controls, he parks in a remote, idyllic spot to admire the scenery. Then the 32nd president encourages his future mistress to take matters in hand herself, so to speak. Cut to a long shot of the sedan gently swaying on its springs.

Casting Murray as FDR may feel like a gamble or a stunt at first, but after a few minutes the rightness of the choice is inarguable. Murray always has been a performer at ease with himself, and that nonchalant self-assurance suits a story more focused on personal than global affairs. At Hyde Park, the Roosevelt summer retreat in upstate New York, he juggles multiple paramours, while dodging the disapproval of Eleanor (smartly tart Olivia Williams) and his mother (Elizabeth Wilson, an artist with arched eyebrows and meaningful silences).

The estate is preparing for some very special weekend guests. As the clouds of war darken in 1939, England’s newly minted King George VI (Bertie, the stutterer) and his bride, Queen Elizabeth, make a momentous visit seeking FDR’s support. Shrewdly aware that Americans don’t like hoity-toity Brits, Roosevelt maneuvers the awkward, formal visitors into attending a picnic where the press will photograph them eating hot dogs. With wily charm he maneuvers the awkward royals to let their hair down for all the world to see. It’s history as a comedy of manners.

Much of the film is told from Linney’s perspective, yet Daisy remains a wallflower. She tells us of their affair, but she scarcely emerges as a memorable character on her own. Williams fares better as Eleanor, wryly impatient with her husband’s dalliances, and Olivia Colman makes a winningly starchy young Queen Elizabeth. If you like your history breezy, here’s a film half as long as “Lincoln” and twice as funny.

“Hyde Park on Hudson” is rated R and is showing at the State Theatre. Visit focusfeatures.com/hyde_park_on_hudson or www.thestatetheatre.org for more information.