Gus Van Sant has spent the past few years making dreamy, amorphous meditations on life and death that seemingly were intended for his hardcore fans, himself, and no one else.

"Gerry," "Elephant," "Last Days," "Paranoid Park" — all beautifully, defiantly languid works of art that most audiences would dismiss for their pretensions.

With "Milk," though, Van Sant boldly returns to mainstream filmmaking with a story that, on its surface, could have been shamelessly mawkish. Instead, he presents the last eight years in the life of Harvey Milk, the slain San Francisco politician and gay rights activist, with a mix of vivid details and nuanced heart.

He's also drawn from Sean Penn one of the most glorious performances ever in the actor's long and varied career.

Penn depicts Milk as a man defined by a charming persistence. He had a way with words and a love of the spotlight and an infinite sense of inclusiveness. He was, in short, a jumble of contradictions, all of which Penn captures gracefully and effortlessly — there's nothing mannerly about his performance, just a deeply engaging immersion.

But it's the thing that defined Harvey Milk primarily, his homosexuality, that got him killed.

From a thoroughly researched script by Dustin Lance Black, the film begins in 1978 with Milk sitting at the kitchen table, speaking into a microphone, telling his life story: "This is only to be played in the event of my death by assassination," he says matter-of-factly, presciently.

"Milk" jumps back and forth through time, from meeting his first real love (a lovely James Franco) and moving with him from New York to San Francisco to opening his camera shop and helping the Castro neighborhood blossom into the gay Mecca it would become. He becomes both den mother and Pied Piper to local kids and lost souls. And he repeatedly runs for the city Board of Supervisors, losing by a smaller margin each time, until he wins after a redistricting in 1977 and uses the seat to fight not just for gay rights but for all civil rights.

The film hits all the important marks but never feels like a typical biopic, a superficial, greatest-hits collection.

Van Sant seamlessly blends archival footage of the time with recreations (the candlelight vigil the night Milk was killed is chilling).

The supporting cast is also crucial, the people who supported Milk and challenged him. Franco seems as comfortable here as he did playing an affable pot dealer in this summer's "Pineapple Express." Emile Hirsch brings a playful energy to the role of Cleve Jones, Milk's protege, and he shares an amusing friendship with Alison Pill as Milk's lesbian campaign manager, Anne Kronenberg.

Josh Brolin, meanwhile, continues to prove he can do pretty much anything. He follows up his funny, evenhanded portrayal of President Bush in "W." with a subtle performance as fellow Supervisor Dan White, the man who pulled the trigger on Nov. 27, 1978, killing Milk and San Francisco Mayor George Moscone at City Hall.