Moments before Clint Eastwood approached the lectern at the Republican National Convention on Thursday night, he asked a stagehand to get him a chair.

Everyone just assumed he was going to sit in it.

Fans that night may have expected to hear fromDirty Harry”: the cool, controlled enforcer, as deft with a quip as with a gun, effortlessly and eternally hip. Instead, they got something closer to Walt Kowalski, the grizzled old cuss of Eastwood’s 2008 “Gran Torino”: raw, unpolished, a little angry and suddenly much older than you realized.

Senior campaign aides said Friday that the unscripted routine by the actor-director — easily the biggest show-biz heavyweight to stand up for a GOP candidate since Frank Sinatra did it for Ronald Reagan — was something of a surprise.

The Oscar winner, 82, spoke off the cuff, having discussed a few talking points with campaign advisers and sketched out some rough remarks but preparing nothing for the prompters. Organizers were comfortable with this setup: At the early August fundraiser in Idaho where Eastwood first came out publicly for Mitt Romney, he delivered suave impromptu remarks that had other guests raving.

Instead, Eastwood’s wacky conversation with the empty chair (standing in for President Obama — and viewed by about 33 million people, according to Nielsen) became an instant Internet meme. His rambling style triggered snark about his health and his age. His old-timey lawyer jokes brought on a wave of triumphant fact-checking/rebuttal (Romney, like Obama, has a JD).

Inside the Tampa convention hall, the crowd roared with delight at Eastwood’s humor. But as Thursday night turned into Friday, Twitter and talking heads piled on the mockery, some claiming Eastwood had managed to upstage and undercut the Republican nominee’s acceptance speech. Ann Romney coolly deemed the actor’s performance “unique” Friday on “CBS This Morning.”

“I didn’t know it was coming,” she said with a nervous laugh.

Don’t look for Eastwood on the campaign trail this fall. His longtime manager said Friday that the star was traveling back from Florida and unavailable for interview requests or comments — and that hewill not speak to the press at all until he hits the promotional circuit for his next movie, “Trouble With the Curve,” opening Sept. 21.

When Eastwood gives his next interviews, manager Leonard Hirshan said,“he’s speaking about the picture, not everything else.”

On Friday, the Romney campaign expressed gratitude for the support of a beloved screen icon — no matter how quirky his delivery.

“He went out and did what actors do sometimes: He did a little improv,” said Stuart Stevens, Romney’s chief strategist.

Convention producers warily eyed the clock as Eastwood ran over his allotted five minutes by six or seven minutes. And the empty-chair gimmick was a complete surprise.

“This was an idea, a moment that moved him, I would say, and he went with it,” Stevens said.

He said Romney, standing backstage, laughed appreciatively through Eastwood’s talk. And Stevens praised Eastwood for hitting key talking points: “For him to go out there and to say that there’s a need to change presidents and that he supports Mitt Romney and talk about 23 million people out of work as he did and talk about when someone doesn’t do their job you need to change, that’s a powerful message.”

Questioned by a reporter from an NBC affiliate in Hampton Roads, Va., Romney’s running mate, Paul Ryan, said, “I think Clint Eastwood was just being Clint Eastwood.”

A rumored Eastwood appearance had been the buzz of the convention from Day 1, after several decades of the Hollywood establishment closing ranks behind Democrats. Entertainers have been especially helpful to the Obama administration, with A-listers such as George Clooney and Sarah Jessica Parker mounting mega-dollar fundraisers for his reelection.

“I know what you’re thinking, you’re thinking: ‘What’s a movie tradesman doing out here? They’re all left-wingers out there!’ ” Eastwood told the convention hall audience Thursday. But there are indeed “conservative people, moderate people” in Hollywood, he said. They just “play it closer to the vest.”

Despite dabbling in politics for years — most notably as the nonpartisan mayor of Carmel-by-the-Sea, Calif., from 1986 to 1988 — Eastwood’s evolving and hard-to-pin-down views have added to his superstar mystique. An occasional Republican voter who allies with many socially liberal causes, he has long resembled a screenwriter’s fantasy of the perfect square-jawed candidate, which may be why many fans project their beliefs onto him. His evocative but cryptic Chrysler ad that aired during this year’s Super Bowl was interpreted by many pundits as a celebration of the Obama auto-industry bailout — although Eastwood, in fact, opposed it.

In an interview with The Washington Post’s Ann Hornaday in November, Eastwood happily talked politics but made no pretense of being a wonk.

Many Hollywood types dabbling in advocacy love to show off their mastery of policy, but Eastwood (“I’ve never been a really astute political person”) uttered the simple hopes and gripes of your typical man-on-the-street interview.

“They all come up now and they all say the same thing,” he said of politicians, Republican and Democratic alike. “They tell you what they want to get in, and when they get in, they all do something different, so you get the futility aspect of it all.”

Although he endorsed Republican John McCain in 2008, Eastwood said he felt good about Obama’s election, at first. “I thought: ‘Well, that’s cool. . . . That’ll be nice for the country and maybe it’ll settle down a lot of racial issues.’ ” Instead, “it kind of went the other way,” he told Hornaday, citing his frustration with how Obama seemed to pick sides in the hot-button dispute when African American scholar Henry Louis Gates Jr. was arrested by a white police officer in Cambridge, Mass. “Just a bad way to jump into it,” Eastwood said.

Romney didn’t seem to be on Eastwood’s agenda last fall. (“I liked that fellow from New Jersey, [Gov. Chris] Christie,” he told Hornaday.) It was just over a month ago that he approached the former Massachusetts governor’s campaign to express his support, and he got invited to a pair of Sun Valley, Idaho, events on Aug. 3.

“He didn’t act like a Hollywood star,” one guest said. The fundraiser, who was granted anonymity in order to speak candidly, noted that Eastwood had no entourage and made no demands. He posed for pictures with police officers and Secret Service agents and sat at a table eating dinner and conversing with other supporters.

“He really wowed both audiences in Sun Valley and could not have been more gracious to the attendees and to Mitt Romney and to the staff,” the fundraiser said.

As for the speech Thursday night, the fundraiser said, “I think the nature of Clint Eastwood is he is unpredictable.”