Weather permitting – the forecast calls for mostly sunny, chance of thunder storms, high of 32 degrees – Barack Obama will crack open a couple cold ones Thursday with two guests: America's most eminent and most aggrieved African-American scholar and the policeman who arrested him.

Most people by now have heard of how Sergeant James Crowley confronted Henry Louis Gates Jr., a Harvard professor, in his own home, after Cambridge police received word of suspicious characters possibly involved in a break-in.

Mr. Gates's behaviour prompted an arrest, quickly dropped, for disorderly conduct. Mr. Obama's comment that police had “acted stupidly” turned a controversy into a frenzy, with the President publicly regretting his remarks.

“The President wants to continue to take down the temperature a bit,” press secretary Robert Gibbs told reporters Tuesday, saying the gathering around a picnic table outside the Oval Office was “an effort and an opportunity to have greater communication, get to know each other, and step back from the circumstances that brought everybody together over the past many days.

“But there's no formal agenda other than cold beer.”

The White House picnic also reveals a president stumbling badly and attempting to recover on an issue that he had previously tried to avoid: the never-healing wound of race.

Race is to America's social discourse as language is to Canada's, multiplied by 10. One out of every nine African-American men between the ages of 20 and 34 is behind bars. Almost 4 per cent of the Latino population is incarcerated. Racial minorities chronically lag in income, education, quality of housing and every other social indicator.

Yet many people viewed Mr. Obama's election as the birth of a post-racial America, a testament to the slow but steady growth of an African-American middle class at least partially integrated within the broader community.

Mr. Obama has, until now, handled this explosive issue with masterful sensitivity. His speech and comments in the wake of revelations of incendiary rhetoric from his former pastor, Jeremiah Wright, defused the issue for all but the most partisan voters.

Throughout the first six months of his presidency, Mr. Obama mostly avoided direct references to his race. He distanced himself from his Attorney-General when Eric Holder declared that the United States was a “nation of cowards,” saying that would not have been his choice of words.

Earlier this month, however, the President gave a stem-winder of a speech celebrating the 100th anniversary of the NAACP.

Speaking of all those who had struggled to advance the cause of civil rights, he proclaimed: “Because of their efforts, I made a little trip to Springfield, Ill., a couple years ago, where Lincoln once lived, and race riots once raged, and began the journey that has led me to be here tonight as the 44th President of the United States of America.”

He raised the roof in a way he hadn't since the election.

No one can know what was on the President's mind when he answered the question about Prof. Gates's arrest at last week's news conference.

“The Cambridge police acted stupidly in arresting somebody when there was already proof that they were in their own home,” he declared, adding, “there is a long history in this country of African-Americans and Latinos being stopped by law enforcement disproportionately. And that's just a fact.”

Except that it was anything but clear that Sgt. Crowley had acted stupidly. The officer conducts racial-sensitivity training at a local police academy. The White House had committed the unforgivable: the President had spoken before he knew the facts.

Interestingly, it was a reporter from Chicago who asked the question. And Mr. Obama first began developing his political skills while working as a community organizer in Chicago's South Side.

Perhaps the question, and the incident itself, evoked those Chicago years, and the years before them, when the President struggled with his own identity and with the complexities of African America, which informed his first book, Dreams from My Father .

In any case, the President clearly realized he had overstepped, admitting Friday, “I could've calibrated those words differently,” and describing the whole affair as “a teachable moment.”

What it might be teaching the President is that even he can put his foot in it. And that it is never a good idea for the President to wade, ill-informed, into a charged controversy rooted in race.