"Callista Gingrich. Karen Santorum. Ann Romney. Now, do you really think our country is ready for a white first lady?" the actor said to roars of laughter from a crowd that included Michelle Obama.
When someone in the audience yelled: "No!" DeNiro continued, "Too soon, right?"
But in a nation where hot-button race issues loom large, Obama's re-election campaign team was quick to distance itself from the remark while Newt Gingrich, the Republican presidential hopeful with a fondness for hyperbole, demanded the president apologize for it.
"We believe the joke was inappropriate," Olivia Alair, campaign press secretary to Michelle Obama, said in a statement.
Gingrich went much further, calling it "inexcusable."
"On behalf of my wife and on behalf of Karen Santorum and on behalf of Ann Romney — I think that Robert De Niro's wrong," Gingrich said at a campaign stop in Louisiana. "I think the country is ready for a new first lady and he doesn't have to describe it in racial terms."
Gingrich, whose branding of Obama as "the food stamp president" has angered many in the black community, called the joke "utterly and terribly unacceptable."
"The president should apologize for him. It was at an Obama fundraiser, it is exactly wrong, it divides the country," he said.
The Twitterverse lit up Tuesday with those on both sides of the argument doing pitched battle.
De Niro is a racist and his remarks are nothing more than Hollywood-approved bigotry, charged those on the right.
"Who knew Robert De Niro was so racist against white people? Another Hollywood hypocrite yapping his mouth off," read one tweet.
De Niro was making sly reference to similar questions once asked about Obama, and those offended should chill out, others countered.
"R Americans really this stupid? Robert De Niro ... was pointing out the hypocrisy of the right-wing's xenophobia," read another tweet.
Even those in the White House press corps weighed in.
"Any serious conversation about being offended by Robert De Niro needs to begin with 'Analyze That,'" tweeted Jake Tapper, ABC News' chief White House correspondent, in reference to the De Niro film about a mobster who goes into therapy.
De Niro's publicist, meantime, said the actor had no intention of responding to the criticism, calling his remarks "obvious satire."
It indeed seems a tempest in a teapot, especially considering the countless debates, news stories, academic papers, cable news panel discussions and public opinion polls that were devoted to a similar question in 2008: Was America ready for its first African-American president?
Apparently some Americans were not.
In the four years of his presidency, racist rhetoric against Obama has flared up on a fairly regular basis. Just this week, the seller of an anti-Obama bumper sticker denied there was anything racist about its slogan: "Don't Re-Nig 2012."
"According to the dictionary, (the N word) does not mean black," Paula Smith of Hinesville, Ga., told Forbes magazine.
"It means a low-down, lazy, sorry, low-down person. That's what the N word means .... And besides, Obama is not even black. He's got a mixture of race. It's his choice of what his nationality is."
Michelle Obama co-hosted the New York fundraiser on Monday night with De Niro, who's married to a black woman. Celebrities in attendance included Beyonce, Harvey Weinstein, Ben Stiller and Whoopi Goldberg, who each paid US$5,000 for tickets.
In Louisiana, Gingrich also compared De Niro's remarks to comments made recently by conservative talk show host Rush Limbaugh, who's still bleeding advertisers after calling a Georgetown law student a "slut" and a "prostitute."
"If people on the left want to talk about talk show hosts, then everybody in the country should hold the president accountable when someone at his event says something that is as utterly and terribly unacceptable as what Robert De Niro said," Gingrich said.
Gingrich ridiculed Obama for calling Sandra Fluke, who testified in favour of the president's contraception policies, to console her following Limbaugh's remarks.
Even fellow presidential candidate Rick Santorum avoided joining Gingrich in outrage over De Niro's remarks, referring to them merely as "sad."
"It's just someone from Hollywood or someone from the entertainment industry just spouting off as they do," he said Tuesday on the Laura Ingraham Show. "It's sad, but I'm not going to bite on that one .... The idea of looking at politics through eyes of race should be over."