Barack Obama sought to confront growing doubts about his electability yesterday by declaring that white, working-class voters would rally behind him if he became the Democratic presidential nominee.

Mr Obama appeared for a televised grilling to answer questions about his inability to attract blue-collar households in the heartland of America. It followed another damaging loss to Hillary Clinton in Pennsylvania last week, which increased concerns among Democrats about whether he is the best candidate to take on the Republican John McCain in November.

Mr Obama’s loss by almost ten points to Mrs Clinton in Pennsylvania, where she again won overwhelmingly among the white working class, bolstered the argument of the former First Lady that the Illinois senator cannot put together a broad enough Democratic coalition in key states to win a presidential election. He lost by the same margin in Ohio in March – a critical election marker – where blue-collar households turned their backs on him.

Mr Obama’s defeat in Pennsylvania came after controversies about anti-American remarks by his former pastor and his own comment that blue-collar voters cling to guns and religion. It has significantly altered the narrative and perceptions of the Democratic battle nine days before the next showdown in Indiana.

Mrs Clinton still has an uphill battle to wrench the nomination from the grasp of Mr Obama because of his insurmountable lead among elected delegates.

Until the Pennsylvania result the main question in the race was whether Mrs Clinton would quit. Now she is being praised for her doggedness and Mr Obama is enduring comparisons to George McGovern, who lost to Richard Nixon in 1972 and who has become known as a candidate who appealed exclusively to the secular, educated wing of the Democratic Party.

Mrs Clinton’s only hope of winning the nomination is to convince a majority of uncommitted super-delegates – the party leaders who will likely determine the race – that her rival is too big a presidential election risk. “The main question is, why can’t he close the deal?”, Mrs Clinton said. “Why can’t he win a big state like this one?”

Appearing on Fox News Sunday Mr Obama was asked why he was having trouble attracting white, working-class support. In an election battle against Mr McCain, Mr Obama said: “Most of those voters will vote for me. I am confident that when you come to a general election and we are having a debate about the future of this country . . . those are voters I will be able to appeal to.”

He conceded that he had to work harder to attract them but highlighted his victories in conservative states such as Idaho. “Look, it’s not like I’ve been winning in states where all they have are black voters or chablis-drink-ing limousine liberals,” he said.

He said that his victories in Virginia and Colorado showed that he could be competitive in Republican-leaning states. He added: “When this started off nobody thought I’d be where we are today. I am relatively new . . . and I am running against the best brand in Democratic politics.”

On Saturday Mrs Clinton challenged Mr Obama to a debate in Indiana with no moderators. The Illinois senator ruled that out. “I’m not ducking,” he said. “We’ve had 21 [debates].”

The Rev Jeremiah Wright, the former pastor to Mr Obama, has reappeared in recent days, granting several interviews.

In one he said that the attacks on him had been unfair and launched for devious reasons. He said that Mr Obama had denounced his remarks “because he’s a politician . . . he does what politicians do”. He is already the subject of a Republican attack advertisement.

Mr Obama said that he had not spoken to Mr Wright to dissuade him from making the appearances.

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