Cam Simpson reports on the Rod Blagojevich case in Chicago.

Conventional wisdom holds that U.S. Attorney Patrick Fitzgerald ordered the FBI to arrest Rod Blagojevich before sunrise Tuesday in order to stop a crime from being committed. That would have been the sale of the Senate seat vacated by President-elect Barack Obama.

But the opposite is true: Members of Fitzgerald’s team are livid the scheme didn’t advance, at least for a little longer, according to some people close to Fitzgerald’s office. Why? Because had the plot unfolded, they might have had an opportunity most feds can only dream of: A chance to catch the sale of a Senate seat on tape, including the sellers and the buyers.

The precise timing of Tuesday’s dramatic, pre-dawn arrest was not dictated by Fitzgerald, nor was it dictated by the pace of Blagojevich’s alleged “crime spree.” It was dictated by the Chicago Tribune, according to people close to the investigation and a careful reading of the FBI’s affidavit in the case.

At Fitzgerald’s request, the paper had been holding back a story since October detailing how a confidante of Blagojevich was cooperating with his office.

Gerould Kern, the Tribune’s editor, said in a statement last week that these requests are granted in what he called isolated instances. “In each case, we strive to make the right decision as reporters and as citizens,” he said.

But editors decided to publish the story on Friday, Dec. 5, ending the Tribune’s own cooperation deal with the prosecutor.

Consider what had been dangling in front of FBI agents and federal prosecutors one day earlier.

Since at least late October, agents had been listening through their headphones to Blagojevich allegedly dream and scheme about a host of potential prizes he could win for the Senate seat, including everything from an ambassadorship to a corporate board slot for his wife. But on Thursday, Dec. 4, he was talking about cash. And a politician talking about trading an official act for cash is a very welcome sound to the ears of an eavesdropping fed. In addition, the Dec. 4 conversation appears to have been the first substantive chat about allegedly selling the seat since Nov. 13.

But on Dec. 4, according to the feds, here’s what they heard: Blagojevich told an adviser he was giving “greater consideration” to one pick for the Senate seat, named “Senate Candidate 5″ by the feds, because of that politician’s willingness to raise money. That man has since been identified as U.S. Rep. Jesse Jackson Jr., the Chicago Democrat affectionately known in his hometown as Triple J.

Jackson has denied any involvement in such schemes and says he never authorized anyone to deal in such a manner on his behalf. He also said Fitzgerald’s office informed him that he’s not a target in the investigation.

Perhaps even more encouraging to the feds listening in on Dec. 4 was what they knew about the first time such a deal was discussed. About a month earlier, Blagojevich was caught on tape describing an approach by an alleged associate of Jackson. Blagojevich’s now-infamous quote about that meeting had been tantalizing. “We were approached ‘pay to play.’ That, you know, he’d raise me 500 grand. An emissary came. Then the other guy would raise a million, if I made him (Senate Candidate 5) a Senator.”

On Dec. 4, with the feds listening in, Blagojevich was allegedly putting this deal back into play.

The conversation resumed later that same day, as Blagojevich allegedly told his brother, a man identified in the affidavit as “Fundraiser A,” that he was “elevating” Mr. Jackson on the list of candidates, because the governor might be able to get something “tangible up front” for the pick.

He told his brother to meet with someone (unidentified by the feds) whom the pair believed to be close to Jackson. He urged his brother to tell this alleged supporter of Jackson that “some of this stuffs gotta start happening now… right now…and we gotta see it. You understand?” He was talking about campaign cash, the feds allege.

Then he allegedly offered his brother one final proviso: “I would do it in person. I would not do it on the phone.”

The next morning, on Friday, Dec. 5, it all came crashing down for the FBI agents underneath the headphones.

The Tribune’s front page screamed: “Feds taped Blagojevich; TRIBUNE EXCLUSIVE: Adviser cooperated with corruption probe, sources say.”

Blagojevich read the same headline. “Undo” that “thing,” the governor allegedly told his brother, according to the FBI. And just like that, the meeting was off, only one day after it had been put back into play.

There appear to have been fears in Fitzgerald’s office that those caught on tape might now seek to “undo” other “things.” Hours were logged over the weekend. Paperwork was pounded out. And before sunrise Tuesday, Blagojevich and his chief of staff were arrested simultaneously. At that same moment, FBI agents also knocked on the doors of witnesses. These were just a few of the people agents wanted to interview before cellphones started ringing across the city and others who had been caught on tape had a chance to get their stories straight.

Had it not been for the Tribune’s Dec. 5 story, the meeting Blagojevich’s brother was arranging might have proceeded. Mr. Blagojevich is quoted as citing the story, in the affidavit, then calling off the meeting. At a minimum, the FBI’s recorders would have been rolling when he reported back. The feds also probably would have tried to bug the session live, or at least to tail the participants and secretly film or photograph them. That’s what feds do. Jurors love video.