Barack Obama is to suspend his campaigning tomorrow for 36 hours so that he can spend time with his ill grandmother in Hawaii.

The Democratic nominee is very close to Madelyn Dunham, 85, whom he calls “Toot”. She brought him up through his teenage years while his mother was in Indonesia.

His spokesman, Robert Gibbs, indicated that the decision to leave the campaign trail with only two weeks left before the election, and some polls tightening, “underscored the seriousness of the situation”. She has been ailing for several months, recently broke her hip, and was said by the family to be in “grave condition”. She is in hospital. Mr Gibbs added: “She has always been one of the most important people in his life.”

Mr Obama cancelled appearances in Iowa and Wisconsin so that he can be with Mrs Dunham in Honolulu before her birthday on Sunday. Along with his wife and children, she is what remains of his close family after the deaths of his father, mother and maternal grandfather, Stanley Dunham.

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When he went to Hawaii on holiday in August Mr Obama was criticised in some quarters. Another temporary departure from the battlefield, even for compassionate reasons, may risk being seen as complacent. It would also cut two days from the fortnight that John McCain has left to land a decisive blow against the Democrat.

Mrs Dunham has featured often in the speeches of Mr Obama. At the Democratic convention in August he talked about how she became the first woman vice-president of her bank “despite years of being passed over for promotions because she was a woman”. He said: “She’s the one who taught me about hard work. She’s the one who put off buying a new car or a new dress for herself so that I could have a better life. She poured everything she had into me.”

He has also cited Mrs Dunham as an example of old-fashioned attitudes towards race when he addressed the issue of his controversial black pastor, the Rev Jeremiah Wright, in Philadelphia in March.

“I can no more disown [Wright] than I can disown my white grandmother,” he said, “a woman who once confessed her fear of black men who passed her by on the street, and who on more than one occasion has uttered racial or ethnic stereotypes that made me cringe.” Mr Obama later described her as a “typical white person who, you know, if she sees somebody on the street that she doesn’t know, there is a reaction”.

He currently has other racially-tinged remarks with which to contend. A Democratic congressman, John Murtha, declared that his base of western Pennsylvania “is a racist area” that could cut the lead of Mr Obama in the state by 4 per cent. “There’s still folks that have a problem voting for someone because they are black,” he added.

Although Mr McCain trails by double-digit margins in Pennsylvania, his campaign is investing heavily in the state that strategists hope to wrest from Democratic hands - and offset expected losses in Iowa, New Mexico and Colorado.

The Republican nominee has made no fewer than seven appearances in Pennsylvania in the past 48 hours. In Bensalem yesterday he delivered another attack on the tax plans and preparedness of Mr Obama for a foreign crisis, saying: “With your help - we’re going to win Pennsylvania, and bring real change to Washington DC.”

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