> George Clooney on Ides of March: 'Politicians have tremendous ego'
Willimon, whose play Farragut North is the inspiration behind Clooney's latest directorial offering, told Digital Spy of his respect for the actor-filmmaker.
"George is a consummate collaborator," Willimon said. "He's whip-smart, brilliant. He's charming, funny and he has vision. He knows how to turn that vision into actual results.
"He's not only an amazing actor, not only an amazing director, but he's also an amazing writer and producer. He brought all those things to the table in getting Ides of March together."
Willimon spent time working for Howard Dean when he unsuccessfully ran for the 2004 Democratic presidential nomination. He witnessed the infamous "Dean Scream", which helped end the politician's chances of leading the Democratic Party.
Willimon said of witnessing Dean's high-pitched wail: "I helped set up the event. I was there and also on the plane that night from Iowa to New Hampshire.
"We didn't know the 'Dean Scream' was going to be replayed 672 times in one news cycle."
The Ides of March opens in UK cinemas on October 28.