He couldn't resist delivering a punch line for fellow voters in Shelburne Falls, Mass. - "I yelled out, `How do you spell plumber?'" - even as he exulted in casting his ballot for the first African-American president.
There's an argument circulating that "The Cosby Show" laid the groundwork for President-elect Barack Obama by presenting an appealing black family, the Huxtables, to young TV viewers who grew up equipped to thwart stereotypes and barriers.
Writer Alisa Valdes-Rodriguez called her theory "the Huxtable effect," a counter to the so-called Bradley effect (named for failed black California gubernatorial hopeful Tom Bradley) of possible hidden racism among white voters.
Ask Cosby, 71, his view of the part his 1984-92 NBC sitcom played as political groundbreaker, and the man who looms large as both a comedian and blunt commentator on black America first offers a measured appraisal.
"I was amazed when the young woman's theory came through," said Cosby. It sounds plausible, he mused, recalling the show's immense popularity and the many times that fans said Cliff Huxtable reminded them of their dad - their white dad.
But he chafes at what he calls the "Karl Rovian" interpretation, referring to the Republican strategist's Election Night comment on Fox News that viewers embraced the Huxtables as "America's family" and not a black one.
"The reason why he's in the White House is Cosby? No, no, no," Cosby said.
He suggests looking beyond the influence of a TV family to that of a real one: the household in which the future president was raised.
He cites Obama's account of being woken early to do his homework and his mother's refusal to brook any complaints. Cosby bows as well to Michelle Obama and her father, who refused special treatment despite multiple sclerosis.
"This is what Michelle and Barack are made of, the things they see" in their parents, he said.
It was Cosby's firm belief in parental responsibility - and aggravation over '80s programs - that shaped the creation of "The Cosby Show," out this week in a boxed DVD set of the complete series.
"I was not happy with what we used to call family TV in those days. ... They had all these shows where you just dropped to one knee and fired, then a car blew up or a plant blew up - all this dopamine-raising violence," he said.
At a time when the sitcom genre appeared near death, the few family comedies that aired were especially dismaying.
"The situation comedies were failing because they had children seemingly who had taken over the house. In a sense, TV comedy writers and producers had decided they would no longer have a family where grown people were making corrections and kids were going through ... `Leave It to Beaver' type things," he said.
The idea for a show where "the parents weren't losing to the kids" was rejected by other networks before NBC executive Brandon Tartikoff bought a revamped version of it, with the original blue-collar family now morphed into affluent professionals.
"The Cosby Show" starred the comedian as a mellow physician who, with his lawyer-wife Clair (Phylicia Rashad), kept a loving, firm hand on their five children.
Tartikoff knew that Cosby, a recording, movie and TV star (with shows including the 1960s "I Spy," in which he was the first black star of a drama series), was funny and likable.
"And Tartikoff also said, `What I like about this show is dignity. The family has dignity,'" Cosby recalled. "And what's odd about it is it was just natural for me. Because what I wanted, the only thing I wanted, was to stop these children on TV from running the house."
Wasn't he also intent on shattering racial stereotypes?
"Look, I'm already black," Cosby said, so pressing the race issue "gets to be stupid after all."
But, he adds, "What I did have in mind was that the images that you see on television are not the behaviors of Americans who are black. Racism is so stupid, but it is and it does exist. Period."
The show was a hit from the start, and from the start it encountered criticism that it failed to portray the difficult lives of many blacks and ignored middle-class issues like assimilation. Defenders said it showed what African-Americans could, and had, achieved.
Its many fans had no reservations about embracing the story of a modern family with bedrock traditions, always infused with Cosby's droll humor and indelibly puckish grin. "The Cosby Show" was the nation's top-rated prime-time program for five years.
And then there's the tantalizing suggestion that the echoes of a sitcom long in reruns changed presidential history - an idea that Cosby can't resist playing with.
"I'm just waiting to see what Bart Simpson's people are going to do at the next election," he said.
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