Only in this hotel room, confronted with the televised replay of the combustible pastor, did the candidate realise the full import of the remarks, his aides say. At the same time, aides fielded phone calls and e-mail from uncommitted superdelegates, several demanding that the candidate speak out more forcefully.

As Obama told close friends after watching the replay, he felt dumbfounded, even betrayed, particularly by Wright’s implication that Obama was being hypocritical. He could not tolerate that.

The next afternoon, Obama held a news conference and denounced his former pastor’s views as “divisive and destructive,” giving “comfort to those who prey on hate.” And so, with those remarks, a tightly knit relationship finally came apart — Wright had married Obama and his wife, Michelle, and baptised their children.

Theirs was a long and painful falling out, marked by a degree of mutual incomprehension, friends and aides say. It began at the moment Obama declared his candidacy, when he abruptly uninvited his pastor from delivering an invocation, injuring the older man’s pride and fuelling his anger.

Obama’s campaign has been striking for its discipline. This is a candidate who prides himself on his coolness and singleness of purpose, not to mention his ability to take on opponents as formidable as Senator Hillary Rodham Clinton and her husband, Bill Clinton, the former president. But Obama discovered one figure who has confounded him, his own pastor.

In recent months, the candidate has tried to distance himself from Wright and his often radical views, even as he felt compelled to understand and explain his former pastor to a larger, predominantly white political world.

As for Wright, he saw a cascade of perceived slights coming from the campaign of a bright young follower whose political ambitions were tugging him away from Trinity United Church of Christ. He saw the church he had founded coming under pressure from reporters and critics, forced to hire security guards. And he made no secret of whom he blamed: Obama’s political adviser, David Axelrod, a white Chicago political operative.

Only a few years ago, the tightness of the bond between Obama and Wright was difficult to overstate. Obama titled his second book, The Audacity of Hope, after one of Wright’s sermons, and his pastor was the first one he thanked when he gained election as a United States senator in 2004. “Let me thank my pastor, Jeremiah A Wright Jr of Trinity United Church of Christ,” Obama said that night, before going on to mention his family and friends.

In this learned and radical pastor, Obama had found a guide who could explain Jesus and faith in terms intellectual no less than emotional, and who helped a man of mixed racial parentage come to understand himself as an African-American. “Our trials and triumphs became at once unique and universal, black and more than black,” Obama wrote in his autobiography Dreams From My Father.