When details of Illinois Gov. Rod Blagojevich’s (D) Senate scam went public, some jumped past his f-bombs to decode the alphabet soup of aliases that investigators assigned to the scandal’s vast cast of characters.

But what’s even trickier than ferreting out the identity of “Senate Candidate 5” is determining what the feds are hinting at when they parcel out a few telltale details amid the cryptic nomenclature.

“There is an informal code. It’s very carefully tailored,” said Rep. Artur Davis (D-Ala.), a former federal prosecutor. “Sometimes there are little subtle hints to be sent.

“You’re trying to quietly reach out to lawyers for potential cooperating witnesses, who read these things very carefully,” Davis explained.

Letting the public in on the investigation can also pry loose information that investigators have not found, said Roscoe Howard, a former U.S. attorney for the District of Columbia.

“It’s kind of like a wildfire. It can chase people out of the woods,” Howard said. “People come dropping on your doorstep saying, ‘I know something about this.’ That’s why you have press conferences.”

It also alerts people that investigators know something, but leave them guessing about how much.

“It’s not whether I’m candidate five or six,” said Washington lawyer Stan Brand. “It’s that I’m mentioned. Then I have to wonder, ‘Am I on tape?’ You’d better start searching your memory and get yourself a good lawyer.”

For the public and press, it’s a “do-you-know” game that plays out with each high-profile indictment. In the Jack Abramoff lobbying investigation, “Representative 1” became Rep. Bob Ney (R-Ohio), who became prisoner No. 28882-016.

The trial of Sen. Ted Stevens (R-Alaska) had “Juror 4,” who lied about a death in the family to get to a horse race. Eliot Spitzer was Client 9, and the petite brunette he hired for the night was known only to us as “Kristen” until the tabloids outed her as Ashley Dupre. But in Rep. Randy “Duke” Cunningham’s (R-Calif.) bribe-to-play case, we found out Brent Wilkes was “Co-conspirator 1,” but we never found out the name of “Prostitute A.”

“That’s the game,” said Brand, a former federal prosecutor who’s now one of the best-known white-collar defense attorneys in Washington. “It’s like ‘Who’s on the D.C. Madam’s list?’ It’ll come out. It always does. Everybody likes to play the game.”

Brand, however, downplays the idea that U.S. Attorney Patrick Fitzgerald and the FBI are dropping hints. They’re just including enough facts to make their case.         

“The prosecutor is not driven by hints,” Brand said. “He’s putting enough facts in evidence to make his case.”

Still, there is big variation in the level of detail attached to the players. It’s not clear why the feds made some people identifiable, while thoroughly cloaking others. And at least for now, they’re not explaining.

Barack Obama, for example, is cited simply as “the President-elect,” though that can describe only one person; same with “Tribune Owner” Sam Zell. Meanwhile famous rich guy Warren Buffett is named outright, albeit in a quote.

Descriptions of “Senate Candidate One” had just about every detail except Valerie Jarrett’s Social Security number. “Senate Candidate 3” comes up only in a brief quote from Blagojevich with no details, and is not named. “Senate Candidate 4” is a deputy governor of Illinois, which narrows it down to three people: Dean Martinez, Bob Greenlee and Louanner Peters.

And the description of “Senate Candidate 5” listed just enough facts to potentially end a political career, or at least Rep. Jesse Jackson Jr.’s (D-Ill.) bid for Obama’s Senate seat.

But it is the players whose descriptions hint at negotiations with the Obama transition that are drawing the most attention in the wake of Jackson’s outing on Thursday. In addition to figuring out who they are, observers are seeking to figure out how big a part they played in Blagojevich’s Senate seat scam.

Incoming Obama chief of staff and outgoing congressman Rahm Emanuel (D-Ill.) is being pressed hard on whether he’s “President-elect Advisor,” though that person is not alleged to have done anything wrong. But Blagojevich clearly indicates he expects to be negotiating with him or her.

And the desires of one “Advisor B” for a “three-way deal” that would leave out Obama’s “fingerprints” has hinted to some that “the President-elect” might not have been so removed from the negotiations.

“Anyone who wants to understand the Blagojevich scandal will have to learn more about Advisor B,” wrote conservative commentator Byron York of the National Review.

There’s also an unnamed “SEIU [Service Employees International Union] Official” even more bluntly portrayed as an intermediary between Blagojevich and the Obama camp.

Spokesmen for Fitzgerald and the FBI in Chicago made it clear last week in interviews that they were not interested in explaining why some people were more identifiable than others.

Officially, the cryptic aliases in the 76-page affidavit by Special Agent Daniel Cain are meant to distinguish between the players in the narrative while protecting the reputation of those not charged, whether or not they’re completely innocent.

As the U.S. Attorneys’ Manual states , “In the absence of some significant justification, it is not appropriate to identify (either by name or unnecessarily-specific description) a third-party wrongdoer unless that party has been officially charged with the misconduct at issue.”

Chicago FBI spokesman Ross Rice said the Bureau is careful not to explicitly identify people who are not being charged, but some information has to be laid out.

“We have to present that complaint to a judge,” Rice said. “You can’t water it down to the point where he can’t make a decision.”