President Barack Obama, right, and Vice President Joe Biden, left, have a beer with Harvard scholar Henry Louis Gates Jr., second from left, and Cambridge, Mass., police Sgt. James Crowley on Thursday in the Rose Garden of the White House in Washington. Through his campaign for the White House and since he’s been in it, Barack Obama has tried to keep discussion of race — his own as well as the nation’s still very uncertain relationship with the topic — at arms’ length.

Washington ? The success of President Barack Obama’s ambitious agenda — from health care and climate change to education — could depend on how quickly he recovers from the sharp drop in support among white voters after criticizing a white policeman’s arrest of a black Harvard scholar.

Obama’s widely publicized effort to defuse the first racial flare-up of his young presidency by inviting the protagonists to the White House last week for beers and conversation ended well by most accounts, even though there were no apologies.

Cambridge, Mass., police Sgt. Joseph Crowley and Harvard scholar Henry Louis Gates Jr. agreed to disagree about the July 16 confrontation at Gates’ home and pledged to meet again.

Obama’s impromptu comments about the incident could become a defining moment. Nearly immediately after Obama’s remark that police had “acted stupidly” in arresting Gates, his approval rating plummeted among whites, dropping over two days from 53 percent to 46 percent in a poll by the nonpartisan Pew Research Center.

If Obama is to have success with the policy changes he wants, he can’t afford to shed white support. Not to mention the disaster that losing the affections of many in the blue-collar, Reagan Democrat constituency would spell for any re-election campaign.

Lawrence Jacobs, director of the Center for the Study of Politics and Governance at the University of Minnesota’s Hubert H. Humphrey Institute of Public Affairs, said he was stunned at how poorly Obama, normally so controlled, handled what Jacobs called “the first major personal debacle for the president.”

“This thing was just hung around his neck and he couldn’t get rid of it,” Jacobs said. “I think he presumed too much. He really started to believe his own press releases on post-racial America.”

Chris Lehane, a Democratic operative in California and a former aide to Al Gore, said Obama prolonged the story by arranging the White House meeting, but was smart to do so because it fits into another narrative that Obama promotes: that he’s a “different kind of president.”

“The politically smart move would have been to call the officer, tell the press, not ask for a meeting and pivot back to health care at a time when the White House needs to regain its momentum,” Lehane said, “while the riskier courageous leader position was to hold the suds summit.”

Greg Strimple, a Republican strategist in New York who advised Sen. John McCain, Obama’s GOP opponent last year, saw Obama’s initial words at the news conference as a calculated play to win points with his base — and it backfired.

“He’s lost the center on economic issues,” he said, citing the big-government label Obama is earning for the massive stimulus package and his health care and energy proposals. “When politicians get in trouble, they always revert to audiences that will clap and cheer the loudest for them. … But they had a fundamental miscalculation on the political strategy of this.”

Regardless how he got himself in the fix, Obama must move on from the national debate the incident prompted.

“The most important thing for Obama is to move on to nonracial topics — health care, for instance,” Jacobs said. “The loss of white support is potentially devastating but it is unclear how sustained it will be, especially if he can enact his legislation.”