TAMPA, Fla. -- For all the internal finger-pointing about Clint Eastwood's rambling conversation with an empty chair Thursday night, the most bizarre, head-scratching 12 minutes in recent political convention history were set in motion by Mitt Romney himself and made possible by his aides, who had shrouded the actor's appearance in secrecy.Romney privately invited the "Dirty Harry" actor to speak after Eastwood had given him a gravelly, full-throated endorsement at a star-studded fundraiser at the Sun Valley Resort Lodge in Idaho this summer. "He just made my day," Romney joked with his donors that night.Thus began an effort by Romney's campaign over several weeks to inject a Hollywood-style surprise into the highly scripted, tightly controlled convention where Romney would formally accept the nomination of the Republican Party to be president.Behind the scenes, Eastwood's bit part was cleared by Romney's top message mavens, Russ Schriefer and Stuart Stevens, who drew up talking points that Eastwood included, in his own way. They gave him a time limit, which he ignored, along with a blinking red light that told him his time was up. The actor's decision to use a chair as a prop was last-minute, and his own."The prop person probably thought he was going to sit in it," a baffled senior aide said Thursday night.Eastwood's rambling and off-color appearance just moments before the biggest speech of Romney's life instantly became a Twitter and cable-news sensation, which drowned out much of the usual postconvention analysis that his campaign had hoped to bask in.It also startled and unsettled Romney's top advisers and prompted a blame game among them. "Not me," an exasperated-looking senior adviser said when asked who was responsible for Eastwood's speech. In interviews, aides called the speech "strange" and "weird." One described it as "theater of the absurd."Ann Romney, who made the rounds of the three network morning shows, hardly pretended that she was happy as she was repeatedly asked about the speech. "I was thrilled for his support," she said on NBC.Gov. Scott Walker of Wisconsin said on MSNBC that he "cringed" as he sat in the hall during Eastwood's performance.The speech was a reminder of how fleeting a successful political moment can be, and how carefully staged events can be upset by an unpredictable turn. And it suggested a slip-up inside the button-down, corporate-style headquarters of the Romney campaign in Boston.Romney advisers so trusted Eastwood, 82, that unlike with other speakers, they said they did not conduct rehearsals or insist on a script or communicate their expectations to him.For Eastwood, the convention speech was a bit part in a career that has had its political moments. Angered by zoning laws he did not like, he served one two-year term as mayor of Carmel by the Sea in California. In 1988, George Bush briefly considered choosing him as his running mate; he picked Dan Quayle instead.During the weeks after Romney extended the invitation in Idaho, the actor's role in the convention lineup was kept secret. On the public schedule, his slot was listed as "to be announced."As the last night of the convention approached, planners tried to keep a lid on the story even as Eastwood's name leaked out on the Internet, hoping his appearance would be the good kind of a surprise, not the bad kind.Another adviser said that several top aides had reviewed the talking points given to Eastwood just a few hours before his appearance. They included a request to mention the millions of people who remain unemployed -- something Eastwood did, though he misstated the number.As actors sometimes do, he improvised.Instead of reading off a teleprompter -- something Eastwood is said to despise -- he pretended to have a sarcasm-filled conversation with President Barack Obama, seated by his side."What do you mean, shut up?" Eastwood said, mumbling to a befuddled audience. A moment later, he stopped again, saying, "What do you want me to tell Mr. Romney?""I can't tell him that. He can't do that to himself," Eastwood said. "You're getting as bad as Biden."Rush Limbaugh called Eastwood's performance "bold." But other members of the party faithful were not so sure. As they flew home from Tampa on Friday, some delegates grumbled that Eastwood was a waste of a prime-time slot that might have been better used to feature other speakers or the biographical video of Romney's life.