Stopping short of offering an actual endorsement, Mr Murdoch made plain his enthusiasm for the Democratic hopefulm when speaking on the fringes of a digital conference in California sponsored by The Wall Street Journal, recently acquired by News Corp.

"He is a rock star," said Mr Murdoch. "I love what he is saying about education. I think he will win and I am anxious to meet him."

Recalling a surprising loss of a safe Republican seat in a Mississippi by-election recently, Mr Murdoch suggested November may see a Democrat landslide. "You have probably the making of complete phenomenon in this country," he noted. John McCain, he said, goes into the election with " lots of problems".

Mr Obama is tantalisingly close to seizing the Democratic nomination. Only three more primary votes remain – Puerto Rico on Sunday, followed by Montana and South Dakota on Tuesday. A potential bump on the road is a meeting tomorrow of the party's rules committee which will consider proposals to reinstate votes cast in Florida and Michigan that were disqualified because both states voted too early.

Mr Murdoch called Mr McCain, the Republican nominee, a "friend of mine" but was unexpectedly harsh in his assessment of him.

"He's been in Congress a long time, and you have to make a lot of compromises. I think he has a lot of problems." He added Mr McCain " doesn't know much about the economy". While he was a "patriot", "he doesn't know much about organising a campaign, it would seem".

Not everyone will be surprised by Mr Murdoch's comments. Earlier this year, his newspaper The New York Post endorsed Mr Obama over Hillary Clinton on the eve of New York's primary election, even though Mr Murdoch had previously appeared to have courted both the former first lady and her husband Bill Clinton. He admitted in California that he had been involved in the newspaper's nod for Mr Obama.

He predicted that the deteriorating economy will aid Mr Obama's bid. " The average American is really getting hurt financially and that all bodes well for him," he said. And while he said the race issue would be a challenge, "it looks like he will overcome that totally".