LOS ANGELES — Clint Eastwood said the idea to use an empty seat as a prop at the Republican National Convention was a spur-of-the-moment decision when someone backstage asked if he wanted to sit down.

In his first interview since his Aug. 30 appearance at the convention to back presidential candidate Mitt Romney, Eastwood told the Carmel Pine Cone that his speech was not only unscripted, it was pretty much spontaneous.

“There was a stool there, and some fella kept asking me if I wanted to sit down,” Eastwood told the weekly newspaper in the California city where he was mayor. “When I saw the stool sitting there, it gave me the idea. I’ll just put the stool out there and I’ll talk to Mr. Obama and ask him why he didn’t keep all of the promises he made to everybody.”

Eastwood’s peculiar, sometimes rambling conversation with an imaginary President Barack Obama in an empty chair set the blogosphere and social media ablaze. Reaction to his appearance generally has split along party lines, with Republicans raving about his stinging rebuke of Obama and Democrats ridiculing him as old, angry and out of touch.

Eastwood acknowledged his presentation was “very unorthodox” but said he knew that would be the case.

“They’ve got this crazy actor who’s 82 years old up there in a suit,” he said. “I was a mayor, and they’re probably thinking I know how to give a speech, but even when I was mayor I never gave speeches. I gave talks.”