John Edwards' first reaction when he learned his mistress may be pregnant was to downplay the chances he was the father, calling the woman a "crazy slut," his former close campaign aide testified Tuesday.

It was the summer of 2007 and Edwards was in the midst of a presidential campaign. Andrew Young testified the former North Carolina senator hatched a plan to funnel money from rich friends to provide the woman a monthly allowance, even though Young said he doubted it was legal.

Months later, as word of the candidate's affair began to leak in the run-up to the crucial Iowa caucuses, Young said Edwards asked the aide to falsely claim paternity of the baby.

Young has been the lone witness during the first two days of Edwards' criminal trial. The 58-year-old Edwards has pleaded not guilty to six counts related to campaign finance violations involving nearly $1 million in secret payments provided by two wealthy donors as he sought the White House in 2008.

Young said Rielle Hunter told Edwards she was pregnant in June 2007, weeks later than the aide originally claimed in a tell-all book published in 2010. Young said Edwards, told him to "take care of it," meaning the pregnancy.

"He said she was a crazy slut and there was a 1-in-3 chance that it (the child) was his," Young testified.

Edwards directed Young to start giving money to Hunter in May 2007, after she threatened to go to the media and expose the affair, the aide said. Edwards suggested asking elderly heiress Rachel "Bunny" Mellon, who had already given generously to the campaign.

Prosecutors showed the jury cancelled checks from Mellon written to her interior designer, who would then endorse them and send them to Andrew and his wife, Cheri. Starting in June 2007, Mellon would eventually provide checks totaling $750,000.

Without telling Mellon what the money would be used for beyond that it was a "non-campaign" expense, Young said she offered to provide $1.2 million over time to help pay for the candidate's personal needs. Under federal law, donors are limited to giving a maximum of $2,300 per election cycle.

"We were scared," Young said. "It was a truckload of money, more money than had ever flowed through our accounts. ... It was crazy."

Young said he expressed concern to Edwards, a former trial lawyer, that they might be violating federal campaign finance laws.

"He told me he had talked to several campaign finance experts and that it was legal," Young testified. "It felt and smelled wrong. But he knew more about the law than we did. We believed him."

Young said Edwards also directed him to use the money from Mellon to provide a monthly allowance to Hunter of between $5,000 and $12,000. The money would allow her to travel and continue to meet up with the married candidate while he was away from his home and now deceased wife, Elizabeth, who had grown suspicious of the affair.

Young will retake the witness stand Wednesday, when the defense is expected to have their first opportunity to cross-examine him.

The baby Edwards fathered, Frances Quinn Hunter, was born in February 2008, right after he suspended his campaign after a series of primary losses. After years of adamant public denials, Edwards eventually acknowledged paternity in 2010. The girl, now 4, lives with her mother in Charlotte.

Prosecutors had phone records showing dozens of calls between Young and Edwards. The candidate often used the phones of campaign staffers to call his trusted aide and mistress to avoid his wife seeing the other woman's number on his bill. Edwards also obtained an extra cellphone his wife didn't know about that they and Hunter called the "Bat Phone," Young said.

In later testimony, Young said in December 2007, Edwards had the idea of Young claiming paternity. It came after reporters from a tabloid tracked Hunter down in the parking lot of a North Carolina grocery store. By that time, non-tabloid media had also started to pick up the trail as the campaign was preparing for the early 2008 primaries.

Edwards said they needed to "give the press something they would understand, an affair between two staffers," Young testified. Hunter had produced several videos documenting life on the campaign trail for Edwards.

Young said Edwards "talked about how this was bigger than all of us," and reaffirmed to the aide he wanted to help the country by getting troops out of Iraq and remaking health care. He also said he didn't want his cancer-stricken wife to have to deal with a scandal before she died.

The Youngs agreed to get the mistress, who was then living in a $2,700-a-month rental home near Chapel Hill, out of North Carolina. They began a cross-country odyssey of travel on private jets and stays in luxury hotels. While they were on the run, the federal indictment alleges that more than $183,000 in bills related to Hunter's care was paid by Fred Baron, a wealthy Texas lawyer who served as Edwards' campaign finance director. Baron has since died.

Young testified that Edwards put him in touch with Baron's people to arrange the details, which included stays at Baron's palatial vacation home in Aspen. As prosecutors highlighted the group's movements, photos of the blue-water resorts and mountain mansion were shown on video monitors around the courtroom.

Baron also sent Young overnight packages stuffed with cash. On included a handwritten note from the wealthy lawyer: "A- Old Chinese saying, use cash, not credit cards!"

When asked why he agreed to claim paternity and care for Hunter, Young said power was the lure.

"I wanted my friend to be president," Young said. "Being friends with the most powerful person on earth, there are benefits to that."

Edwards has denied knowing about the money provided by Mellon. In opening statements on Monday, his defense lawyer Alison Van Laningham said the Youngs siphoned off the bulk of the money to pay for the construction of their $1.5 million house near Chapel Hill.

The indictment filed by the U.S. Justice Department last year recounts more than $933,000 in unreported payments from the two campaign donors who had already given the maximum contributions allowed by law.

Defense attorneys say even if Edwards knew about the secret payments from Mellon and Baron, they don't fit the legal definition of political contributions because they were not meant to influence the election. Instead, they say, the payments were gifts meant to hide Edwards' affair from his wife, not voters.

If convicted on all six counts, Edwards faces a maximum penalty of 30 years in prison and as much as $1.5 million in fines.

Edwards sat silently in the courtroom Tuesday as prosecutors played several voicemails he and Baron had left on Young's cellphone in December 2007 and January 2008. At that time, Edwards was in the heat of the presidential primaries and was constantly in the public eye.

Though none of the voicemails played for the jury contained evidence that was in itself damning, it illustrated that Edwards was in frequent contact with Young and Hunter while they were on the run. Young said Edwards expressly told him not to inform him of their exact location, because the candidate "didn't want to have to lie if he was asked about it."

Asked by a prosecutor why he began keeping the voicemail and notes now being used as evidence against his former boss, Young replied: "If I didn't have these, nobody would have believed me."

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Follow AP writer Michael Biesecker at twitter.com/mbieseck