Barack Obama won a convincing victory in the US presidential election as the man who could deliver “change you can believe in”.

The President-elect emerged, however, from a city where political corruption has been rife since before the time of the gangster Al Capone. As Robert Grant, the FBI agent who arrested Mr Blagojevich, said yesterday: “If [Illinois] is not the most corrupt state in the United States, it is certainly one hell of a competitor.”

Mr Blagojevich is the fifth Illinois governor to be indicted for white-collar crime since 1960. Three of his predecessors were convicted.

What makes the prosecution of Mr Blagojevich potentially nettlesome to Mr Obama is the President-elect's lengthy relationship with the Syrian-born fixer Tony Rezko. During the election campaign, the US press largely turned a blind eye to Mr Obama's ties to Rezko, who was convicted in June of running a scheme where companies seeking state business had to pay kickbacks to him or Illinois politicians. The “pay-to-play” schemes form the basis of some of the allegations against Mr Blagojevich.

Mr Obama has admitted that Rezko was a friend - but was also one of his earliest campaign contributors when he began his political career in state politics in the mid-1990s.

An associate of Rezko told The Times that Mr Obama telephoned Rezko frequently during this period to discuss state politics. Mr Obama had already graduated to national politics, by winning a US Senate seat, when he enlisted Rezko's help in buying his current house in 2005 at a $300,000 (£200,000) discount.

Mr Obama has never been implicated in Rezko's corruption, even though it emerged that Rezko had channelled two $10,000 contributions to Mr Obama's Senate campaign from funds allegedly derived from kickbacks. The President-elect has not been accused of any wrongdoing. But the resurgence of interest in Rezko's case with the arrest of Mr Blagojevich cannot have been welcome news, if only because it highlights how Mr Obama, too, dealt closely with a corrupt character on his way up the greasy pole of Illinois politics.

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