But if Arnold Schwarzenegger was miscast in his new supporting role - a pro-choice, gun control liberal in a deeply conservative setting - then both he and the audience masked it well. For when the former action hero and current governor of California took to the stage of Madison Square Garden the faithful were ready for him.
The delegates' posters, waved to the cameras, had been switched from proclaiming A Nation of Courage to People of Compassion. An array of female and minority speakers had been lined up to soften the edges of a reputation the party fears may be just too hard for many moderates and undecided women.
And while the undecideds watched on television, the devoted looked on in the audience. Valerie White, from Asheboro, North Carolina, had had each of her nails decorated with the American flag, and her favourite sequinned vest was in his honour. "He's what America is all about," she said. "You can come to this country and be successful."
As though the president's address today were strictly B-list, Patti Gaines, from Alabama, told the New York Times: "From the time we found out about it, that's who I wanted to make an effort to come and see. I wanted to see Laura, too. It was nice that they were on the same night, but he was the main reason."
Mr Schwarzenegger's performance did not disappoint. He brought star quality to a party now renowned for its hostility to Hollywood. "Governor Schwarzenegger is someone people pay $8 to see - in droves," said the Republicans' chairman, Ed Gillespie, explaining how Arnie's fame could help Republicans reach beyond the committed to the star-struck.
And so the governor did his party pieces. Rehashing lines from his movies, he recounted how a wounded soldier told him, "I'll be back". He told the crowd "America was back from the attack on our homeland", and the Democrats should have called their convention "true lies".
Not surprisingly, his biggest cheers were for his least moderate statements. When he branded those questioning the performance of the economy as "economic girlie men" the crowd went wild. When he told them he had been inspired to become a Republican by Richard Nixon, they cheered heartily. When he said "if you believe that this country and not the United Nations is the best hope for democracy, then you're a Republican", they chanted "U-S-A, U-S-A".
But in a speech in which he used personal narrative - from immigrant to bodybuilder to film star to politician - to champion the American dream, this was more about his own political prospects than about George Bush. In a 23-minute speech, he mentioned America 47 times, used the word Republican 15 times and referred to President Bush by name six times. As the New York Post columnist, Linda Stasi said, "whoever put those [Bush] twins on after Arnold needs to be beaten severely about the head and neck".
For the sorority goodtime girls this was their coming out parade, the first time they had publicly supported their father in politics. Giggling through a litany of feeble one-liners, the sole task of the two 22-year-old daughters of Mr Bush was to introduce their father on video-satellite who would then introduce their mother, Laura. The crowd shuffled awkwardly in their seats at their attempts to be cute.
As more than a thousand of their peer group were being arrested in the city, the Bush girls gleefully admitted they were "not very political" before cracking jokes about their underage drinking and telling the world that their parents' pet name for each other was Bushie.
Compassionate conservatism would have sent them back to their temporary hangout, the Union League Club, and to bed with a large Cosmopolitan. CNN's anchor woman summed it up for many when she turned from the sister act to camera to confess: "I'm not sure what that was about."