Former Illinois Governor Rod Blagojevich "didn't take a dime" but trusted the wrong people, his lawyer said as the trial began.
Mr Blagojevich faces 24 charges, including attempting to sell President Barack Obama's vacant Senate seat, racketeering and attempted extortion.
If convicted, the Democrat could be sentenced to 415 years in prison and ordered to pay fines of $6m (£4.1m).
Mr Blagojevich, who was impeached last year, has strongly denied the charges.
In an opening statement lasting one hour and 45 minutes, Lawyer Sam Adam Jnr said that Mr Blagojevich had been tricked by those close to him.
He said Antoin "Tony" Rezko, who has since been convicted on corruption charges, helped raise money for many political candidates - including Mr Blagojevich
But no fraudulent money had gone into Mr Blagojevich's campaign or into his pocket, he said.
"You have to be comatose not to figure out how to get a dollar out of $52 billion (£36 bn)," said his lawyer, Sam Adam Jr, referring to the state budget.
"But who didn't? Him!" he said.
Mr Adam said Mr Blagojevich will also take the witness stand, as well as his wife, Patti.
Prosecutors said they will play wire-taps which they claim prove Mr Blagojevich's guilt.
"You will hear him say in vivid terms how valuable this Senate seat was to him," prosecutor Carrie Hamilton said.
She quoted Mr Blagojevich as saying: "I mean, I've got this thing and it's.... golden... I'm not just gonna give it up for... nothing."
Mr Blagojevich, who was twice elected governor, has said he wants the court to hear 500 hours of taped phone conversations to prove his innocence.
He was arrested 18 months ago along with his brother and co-defendant, Robert Blagojevich.
He is also accused of wire fraud and others charges which relate to demanding donations from potential campaign contributors in exchange for favours.
His predecessor as Illinois governor, Republican George Ryan, was convicted of racketeering and wire fraud and is now serving a six-and-a-half year sentence.