Jason Biggs has revealed that he found starring in political drama Grassroots "a challenge".
The American Pie star, who plays campaign manager Phil Campbell in Stephen Gyllenhaal's film, admitted it's easier to hide behind a comedy and he found it a struggle to rein in his instinctive desire to go for the joke.
"Humping a pie, getting naked, that's fine. People ask me if that embarrasses me, but making a fool of myself on screen is not me being vulnerable," he said.
"Me being vulnerable is Grassroots, and showing my emotional or sensitive side."
The 34-year-old said giving a subtle performance was tough.
"Recently, the kind of movies that I've done, certainly the comedy, you tend to go for the joke. There's more in this film. Stephen alluded to the heart of the character I play, and even in the broader comedies, I've always tried to play it as grounded and as real and as subtle as possible," he said.
"The subtlety was interesting, because there was a lot for the character to convey emotionally without a lot of dialogue and with quite a bit of restraint."
Based on a true story and Phil's book Zioncheck For President, Grassroots tells the tale of the opinionated and eccentric Grant Cogswell, played by Avatar's Joel David Moore, and his 2001 campaign for Seattle City Council.
:: Grassroots is released in cinemas today (November 9).