The trailer for Gus Van Sant’s latest movie, Milk, has just gone live, and it looks mighty promising.

The story of Harvey Milk, who was the first openly gay mayor of San Francisco in the 1970s and the events that led to his eventual murder at the hands of disgruntled colleague Dan White, it’s a movie that could well be a contender for Oscars come next year.

Van Sant can experiment with the best of them, but for this movie – which, politically, culturally and socially you’d imagine is pretty close to his heart – he seems to have adopted the more conventional style of his work on, say, Good Will Hunting.

Ultimately, though, this is a movie that will be driven by the power of its performances, and the trailer does enough to hint that the ensemble that Van Sant has assembled will be hugely impressive, from Josh Brolin as the bitter and homophobic White, to James Franco as Milk’s lover (does this mean, after Pineapple Express, that a drama for him is playing against type?), and an unrecognisable Emile Hirsch.

But Penn – sporting an alarming side parting – is the main draw here. Milk is a role that has to be played just so – too flamboyant and you might as well cast the guy who played the security officer in Meet Dave; too serious and the movie is in danger of becoming a lecture. But Penn looks like he has nailed both Milk’s joie de vivre and charisma, but also the doubts and courage that raged within as he suffered death threats on his way to the top job in SF.

As ever, don’t take our word for it – pop along here and see for yourself.