NEW YORK — In the aftermath of Clint Eastwood’s perplexing and ridiculed “invisible Obama” monologue at the Republican National Convention, conservative blogger Moe Lane summed up what many on both sides of the political divide are thinking.

“The term ‘surfing on the edge of the catastrophe curve’ comes to mind,” Lane wrote at RedState, concluding the bit that had the 82-year-old Hollywood icon talking to an empty chair did work but, “I would not recommend that the GOP make it a habit.”

Celebrities have courted politicians, and vice versa, since the dawn of Hollywood, but what happens when the alliance backfires, when the two worlds are suddenly speaking different languages?

The crowd Thursday night at the Tampa Bay Times Forum, just ahead of Romney’s “speech of a lifetime,” greeted the Eastwood Moment with hearty laughter and applause, a welcome break of levity on the last day of a tightly choreographed convention.

But behind the scenes, Romney’s campaign staff didn’t find it so humorous. Asked about it immediately after the convention concluded, a half-dozen staffers said little. The campaign quickly went into damage control.

Unlike every other convention speaker, the teleprompter in the hall wasn’t used during Eastwood’s speech, which had him lampooning President Obama as if he were there.

In this world of oversharing, when the like-minded or contrary are only a tweet away, social media blew up over Eastwood’s confusing convention appearance, along with political-pundit quarterbacking on both ends of the spectrum.

“It … was odd. Not consistently terrible as some argued,” observed National Review’s Jim Geraghty. “I have no doubt some folks loved it. It may very well have actually moved some votes. But boy, did it get weird at times.”

Discomfort or mere awkwardness aside, it’s rare for a celebrity endorsement to backfire in a big way, said Steve Ross, a professor of history at the University of Southern California who has studied the impact of star endorsements in political campaigns.

While some stars, such as Jane Fonda, have proven toxic (she went to North Vietnam during the war in 1972), Eastwood carries enough gravitas and respect that he will get more people to pay attention to Mitt Romney, Ross said.

Yet freewheeling celebrities do bring their risks:

Though far from a catastrophe, during a stop at an Obama fundraiser in March, Robert De Niro found himself at the center of a White House apology over a joke about candidates’ wives.

“Callista Gingrich. Karen Santorum. Ann Romney. Now do you really think our country is ready for a white first lady?” De Niro asked the crowd, according to a White House pool report.

Gingrich howled. The White House and the actor apologized.

George Clooney, the Hollywood darling of the Obama administration, got arrested outside the Sudanese Embassy in Washington that same month, managing to suck up plenty of limelight after traveling to the troubled region himself and testifying before the Senate.

Linking celebrities to candidates was a process that started in the late ’20s, when movie stars were sent on the road to stump with politicians, Ross said. The idea was to draw in more people — many of whom would leave after seeing the star but others who would stay and listen to the candidate’s message.

Capitalizing on celebrity culture to capture new votes, especially among the undecided, was the value, he said.

“This has been the key idea whether it was 1928 or 2012 with Clint Eastwood,” Ross said.

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