CHICAGO — There’s no evidence Barack Obama knew that Rod Blagojevich may have sought to trade an appointment to the president-elect’s vacated U.S. Senate seat for a Cabinet post or other top administration job, the judge at the ousted Illinois governor’s retrial said Monday.

The issue arose at the start of a third week of testimony, which otherwise turned sharply away from the Senate seat charge toward accusations that Blagojevich attempted to shake down executives for campaign cash.

A sometimes-contentious day of testimony began with Judge James Zagel refusing a request from defense lawyers to let them look at FBI interview notes with Obama to see if the Democrat from Chicago ever reported to authorities that Blagojevich had tried to trade the Senate appointment.

“In all honesty, it is possible that the victim of this was busy with other matters at the time,” Zagel said about Obama, who is not accused of any wrongdoing in the case. “There is nothing to indicate that he was aware of” any attempted trade.

The defense had hoped to use the notes to show Obama never saw himself as a victim. Zagel said it was irrelevant whether Obama did or didn’t: Bank tellers might not know their bank is being robbed, he argued, but that doesn’t mean there was no crime.

Blagojevich, who has denied any wrongdoing, faces 20 counts, including several linked to the Senate seat allegation. Jurors at his first trial last year deadlocked on all but one charge, convicting him of lying to the FBI.

Prosecutors continued to get witnesses on and off the stand much faster than at the first trial. That could mean the government finishes its case within a week or two.

The chief executive of Children’s Memorial Hospital, Patrick Magoon, spent just 30 minutes testifying Monday about how Blagojevich allegedly tried to squeeze him for a $25,000 contribution. He spent hours on the stand at the first trial.

Earlier Monday, the defense laid into an old Blagojevich friend and former adviser during cross-examination.

Occasionally raising his voice, defense attorney Sheldon Sorosky suggested that John Wyma had betrayed Blagojevich by agreeing to work as an informant for the FBI in 2008.

“So, you elected to be a spy against your friend for the government?” Sorosky asked, clearly attempting to taint Wyma in jurors’ eyes. Zagel sustained a prosecutor’s objection before Wyma could answer.

Sorosky also picked up on a favorite defense refrain, telling Wyma that talk by Blagojevich about pressuring executives for campaign cash was only that — talk.

“This was just conversation between two pals, right?” he asked — in a question Zagel also ruled out of order.

Sorosky repeatedly raised the ire of the judge and prosecutors, including by once suggesting that federal agents employed underhanded tactics to press Wyma to turn on his longtime friend.

“With all due respect, I am not putting the government on trial,” Sorosky shot back after Zagel admonished him for the line of argument.

“Oh, yes you are!” Zagel snapped, momentarily losing his cool. “Do not do that again.”

Another time, Sorosky even tried to ask Wyma the meaning of a four-letter curse word that Blagojevich is heard using on one FBI wiretap recording played to jurors. Zagel also disallowed that question, saying Wyma can’t be considered an expert on four-letter words.