Forgive the Oscar prognosticating, but this year's best actor field is a crowded one (and the Academy may as well engrave "Daniel Day-Lewis" on the statuette right now). Yet it would be a shame if Bill Murray's performance as Franklin Delano Roosevelt in the charming and wistful Hyde Park on Hudson gets overlooked.

A deceptively subtle portrayal in which the mostly deadpan comic star disappears beneath the pince-nez and the snappy brim of a presidential fedora, Murray offers a fascinating glimpse into a complex and charismatic figure during a pivotal weekend in June 1939, when Roosevelt and the first lady (a stellar Olivia Williams) played hosts to the British royals. King George VI (Samuel West) - yes, the stuttering monarch made famous again in The King's Speech - and his wife, the Queen Consort Elizabeth (Olivia Colman), are motorcading through the rolling green of Dutchess County, N.Y., en route to the country getaway of the 32d president. War with Hitler is imminent, and the king is on a mission to get FDR on England's side.

Hyde Park on Hudson, nimbly directed by Roger Michell, offers more than just an intriguing historic footnote, however. The movie aches with heartbreak and longing, orbiting as it does around one Margaret Suckley (Laura Linney), a distant cousin of the president. This shy and socially awkward woman lives with her frail aunt (Eleanor Bron) not far from Roosevelt's Hyde Park hideout. The film follows her treacherous tumble into an affair with the commander in chief, who's hobbled by polio and looking for an escape from the daunting worries of the Great Depression, of crises foreign and domestic.

"He said I helped him forget the weight of the world," Linney's Margaret voice-overs - a narration based on a wealth of private journals Suckley poured her soul into, and that went undiscovered until her death. With Eleanor Roosevelt pretty much out of the picture (she made no secrets about being a lesbian), a romantic liaison with the president was not the scandal it might have been. Franklin and Margaret were discreet, the press corps honored the president's privacy - a protective pack of camera-snapping, notebook-flapping newshounds - and there were far more important matters to convey to the nation.

(In this respect, the contrast between the way the media covered FDR and, say, the way it went about reporting the Clinton-Lewinsky scandal is marked.)

But as the relationship between the president and his cousin developed, Margaret fell more and more in love, lurking in the corners of Hyde Park and looking on admiringly as he dispatched his staff, or dealt with Eleanor, or with his mother (Elizabeth Wilson). And, of course, with the king and queen.

There's a long and revealing scene between FDR and King Bertie, having retreated to the president's study after a formal dinner. They drink and smoke and discuss their worries, their wives, and their respective infirmities. FDR equates his handicap - the polio that left his legs in braces and that necessitates his being carried, sometimes, like a child in the arms of a strapping aide - with the speech impediment that makes it difficult for the king to convey his thoughts clearly.

In short, the two men bond. And we learn much about the president, and the king, as they do so.

Margaret learns a lot about Franklin, too, and it's not all good. Hyde Park on Hudson has its sunny, whimsical side - the picnic of hot dogs and Indian songs that leaves the king and queen confounded, suspecting they're being made fools of - but there's a deep melancholy running through this pretty period piece of a film.

Murray and Linney are terrific together (and apart), their notes pitch perfect, and the supporting cast is good all around. Michell's choice of music, too, is dead-on: pop songs of the day ("I Don't Want to Set the World on Fire," "If I Didn't Care") that add trenchant irony to scenes. The tunes, like the film itself, come across as blithe and neat, but reveal far messier stuff underneath.EndText