John Edwards arrived at a federal courthouse in North Carolina Monday morning with his freedom on the line, as attorneys prepared to argue whether the cover-up of his affair with Rielle Hunter violated campaign finance law. 

The day of opening arguments comes more than four years after the former U.S. senator ended his Democratic presidential campaign. While the lurid details of his affair dominated the headlines going into the summer of 2008, the focus of the trial is strictly the money trail. 

At issue is whether nearly $1 million from two wealthy contributors used to hide Edwards' pregnant mistress was intended to preserve his "family man" image during the 2008 presidential campaign -- or whether it was merely intended to prevent his wife and children from finding out about the affair. That could make the difference in whether the jury determines the money was an illegal campaign contribution, as prosecutors argue, or whether the money simply represented some very generous personal gifts. 

The case will also examine whether Edwards even knew about the payments, which were made on his behalf by his national campaign finance chairman, the late Texas lawyer Fred Baron, and campaign donor Rachel "Bunny" Mellon, a now-101-year-old heiress and socialite. Each had already given Edwards' campaign the maximum $2,300 individual contribution allowed by federal law. 

"The prosecution is arguing for a broader view of what counts as a campaign contribution," said Ron Wright, a criminal law professor at Wake Forest University. "The defense would like a stricter, more traditional definition of campaign contribution." 

Edwards is accused of conspiring to solicit the funds and faces six felony counts -- each carrying a maximum sentence of five years in prison and a $250,000 fine. He has pleaded not guilty. 

U.S. District Court Judge Catherine C. Eagles, who was appointed in 2010 by President Obama, will preside. She said she expects the proceedings to last about six weeks. 

Edwards denies having known about the money, which paid for private jets, luxury hotels and Hunter's medical care. Abbe Lowell, the well-known Washington lawyer who is representing Edwards, has said that even had Edwards known about the secret payments, his actions wouldn't amount to a crime under federal law. Lowell has said in court that the government's case relies on flawed legal reasoning, that the grand jury process was tainted and that the Republican federal prosecutor who led the investigation was motivated by partisanship. 

But prosecutors will seek to prove he sought and directed the payments to cover up his affair, protect his public image as a "family man" and keep his presidential hopes viable. 

Much of the money at issue was funneled to Andrew Young, a former campaign aide once so close to Edwards that Andrews initially claimed paternity of his boss's illegitimate child. Young and his wife invited the pregnant Hunter to live in their home near Chapel Hill and later embarked with her on a cross-country odyssey as they sought to elude tabloid reporters trying to expose the candidate's extramarital affair. 

Young later fell out with Edwards and wrote an unflattering tell-all book, "The Politician." Young and Hunter recently ended a two-year legal battle over ownership of a sex tape the mistress recorded with Edwards during the campaign, agreeing to a settlement that dictates that copies of the video will be destroyed. 

Young is expected to be a witness for the prosecution, while the defense is likely to call Hunter to testify. After years of adamant public denials, Edwards acknowledged paternity of Hunter's daughter, Frances Quinn Hunter, in 2010. The girl, now 4, lives with her mother in Charlotte. 

It has not yet been decided whether Edwards, a former trial lawyer once renowned for his ability to charm jurors, will testify in his own defense. 

Fox News' Jonathan Serrie and The Associated Press contributed to this report.