Former US Vice-President Al Gore picked up an Oscar for his climate change documentary, An Inconvenient Truth, at the 79th Academy Awards ceremony.
Earlier on, while on stage with actor Leonardo DiCaprio, he teased the audience by pretending he was about to announce a second White House bid.
His joke followed speculation that an Academy Award would help the politician join the 2008 presidential race.
Martin Scorsese's The Departed won best picture at the ceremony.
DiCaprio, who was quizzing Mr Gore on stage during the Oscars ceremony, asked him if he had "any kind of major, major announcement" to make.
Mr Gore, who lost to George Bush in the 2000 US elections, said: "Even though I honestly had not planned on doing this, I guess, with a billion people watching it's as good a time as any.
"So, my fellow Americans, I'm going to take this opportunity right here and now, to formally announce my intention..."
However, he never got to finish his sentence, as the music used to make winners wrap up their speeches cut in and drowned him out.
He left the stage with DiCaprio laughing.
Gore's acceptance speech, however, was more serious where he spoke of global warming.
"People all over the world - we need to solve the climate crisis. It's not a political issue, it's a moral issue," he said.
"We have everything we need to get started with the possible exception of the will to act. That's a renewable resource - let's renew it."