A day after Barack Obama sealed the Democratic nomination for president, a corruption scandal involving a fundraiser who once bankrolled his campaign resurfaced to slightly dampen the festivities.

Chicago businessman Antoin "Tony" Rezko, 52, was convicted Wednesday of fraud, money laundering and aiding and abetting bribery in a plot to squeeze illegal payoffs out of firms hoping to do business with the state.

Republicans are already capitalising on Rezko's ties to Obama, even though the presumptive Democratic presidential nominee is accused of no wrongdoing and his name was barely mentioned at trial.

"Today's verdict and Obama's friendship with Rezko raises serious questions about whether he has the judgment to serve as president," Robert M. "Mike" Duncan, chairman of the Republican National Committee, said in astatement.

Rezko’s S8 million bond was

revoked and he was taken into federal custody after the verdict in the nine-week trial that exposed a corrupt culture of payoffs and campaign finance abuses plaguing Illinois politics.

US Attorney Patrick J. Fitzgerald said the verdict represented "an antidote to the poison of corruption" that trial testimony alleged included the fixing of state boards that controlled a $40 billion pension fund and made major decisions about million-dollar hospital construction.

The trial included explosive testimony about all-night drug parties involving the government's star witness and allegations that Gov. Rod Blagojevich personally discussed a state job for a campaigncontributor.

Rezko has known Obama since he entered politics, raised money for his Illinois campaigns and was involved in a 2005 real estate deal with him. Obama has donated $150,000 in Rezko-related contributions to charity.