Federal prosecutors have described Illinois Gov. Rod Blagojevich's alleged scheme to sell Barack Obama's former U.S. senate seat to the highest bidder as abject, blatant corruption.
But, for the senate candidates seeking to fill the vacant seat, the case touches on a murky area between accepted political favor trading and illegal conduct.
The controversy over the seat has embroiled Congressman Jesse Jackson Jr., who emerged Wednesday as one of several candidates allegedly mentioned by Blagojevich in conversations recorded by the FBI as someone the governor apparently thought would pay money to be appointed to the senate.
"There are gray areas when you say, 'Hey I'll be supportive of you, I'll vote for your bill if you vote for mine. If I'm elected, I'll support your initiatives.' That's politics," said Ron Safer, the former head of the criminal division of the U.S. Attorney's Office in Chicago.
"I will pay you $500,000 for the Senate seat, that's black and white," he said. "It's black, dark black. 'Appoint me and I'll get a fundraiser together and I guarantee you you'll get $1 million' -- that's bribery."
Jackson, the son of civil rights leader the Rev. Jesse Jackson, has denied any wrongdoing. He has not been accused of any misconduct and said he has been told by prosecutors that he is not a target of the investigation.
A certain amount of goodwill is implied in any political appointment, said Chris Lehane, a Democratic strategist and former staffer in the Clinton White House.
"There is an implicit understanding in a situation where you're making an appointment, particularly a U.S. Senate seat, that the person you select is going to appreciate that and will reflect a degree of loyalty going forward," he said.
"But it's not something you ever explicitly have a conversation about," he said. "The reality is there is a bright shiny line that you just don't go over."
Others who work in politics were not as sure that the line is that bright. "Is it wrong to say I want this job and by the way I'll raise money for you and the party, I'll help your candidates? That's the normal course of politics," said New York political consultant Hank Sheinkopf.
"It depends on the timing and the real intent. It's one thing to raise money for a political campaign, it's a different thing to say I'll give you money for personal use."
Jackson, identified as Senate Candidate 5 in the investigation , might face criminal charges if prosecutors can prove he authorized one of his associates to offer money in exchange for Barack Obama's Senate seat, former federal prosecutors say.
But, any agreement about the senate seat would need to go beyond normal political horse-trading in order to be criminal, attorneys say.
"There's horse-trading that's accepted practice," said Patrick Collins, a former federal prosecutor who successfully prosecuted former Illinois Gov. George Ryan. "Perhaps one line is whether there is a personal benefit attached to the demand on both sides. What makes it potentially corrupt is, appoint me and I'll get you some cash in return."
Political consultants said the kind of alleged quid pro quo arrangement described in the Blagojevich case is unusual.
"People raise a lot of money for them and then they appoint those people. That happens all the time," said Tad Devine, a senior advisor to Al Gore and John Kerry in their presidential campaigns.