MCT

While John Edwards was in the last stages of his 2008 US presidential campaign focusing on the poor, his pregnant mistress and political aide were exploring the wealthy upper side of Edwards' "two Americas".

The first two days of testimony in the criminal trial of the one-time Democratic hopeful have focused on posh hotels and resorts, big houses in exclusive neighbourhoods and the super rich who can dole out thousands of dollars at short notice.

Andrew Young, the former campaign aide, was on the witness stand in a federal courtroom all Tuesday and much of Monday. His testimony has detailed how he spent the largesse of rich supporters first to mollify Edwards' restless mistress, Rielle Hunter, and then to hide her from tabloid reporters once she became pregnant.

Young moved from house to house and hotel room to hotel room on a harried cross-country odyssey with a pregnant Hunter, his wife Cheri, and, for part of the journey, the three Young children.

They stayed in pricey hotel rooms and luxurious estates in Florida, California and the Colorado resort town of Aspen. They lived in the gated Governor's Club in Chatham County, North Carolina, and eventually moved in to a $US1.5 million ($A1.46 million) house the Youngs built on a lot just outside Chapel Hill, North Carolina.

Young testified that Hunter insisted on staying in the best rooms of fancy hotels that had the "right energy". She shopped at Neiman Marcus and fancy food stores and had people run errands for her while living in exclusive neighbourhoods. At one point, Young said, Hunter tried to arrange a deal so she could stay in a glitzy Aspen holiday home complete with a first-floor pool that lit up at night like the constellations.

Edwards, 58, is accused of conspiring to secretly obtain more than $US900,000 ($A875,358) from two wealthy supporters to hide his extramarital affair with Hunter and her pregnancy from the media. He has pleaded not guilty to six charges related to violations of campaign financing laws.

Young's testimony has offered two starkly different portrayals of Edwards - a politician who in public spoke of Olympian idealism and in private could be cold enough to turn his back on an aide and mistress, whom Young said he called a "crazy slut".

Young testified on Tuesday that Edwards tried on more than one occasion to distance himself from Hunter, the first after his wife Elizabeth Edwards intercepted a phone call and insisted she be fired from her position as campaign videographer.

Prosecutors used phone records, voicemail messages, photocopies of large cheques and handwritten notes with testimony from Young as they laid out their case.

Defence lawyer Allison Van Laningham said on Monday in her opening statement that Edwards had "committed many sins, but no crimes".

Young said that he participated in a scheme in which he solicited vast sums of money from the wealthy to help support Edwards' mistress because he was worried about his own future.

When asked by prosecutor David Harbach why, even with the support of his wife, he claimed paternity of Frances Quinn, the daughter born to Hunter and Edwards, Young said:

"By this point we were in very deep. We had been taking care of and hiding his mistress and lying to a great deal for people. We believed in the causes. I wanted my friend to be president, I can't deny that. Being friends with the most powerful person on Earth, there's a lot of benefits that go along with that - for yourself, for your family."

Young said he dreamed of working in embassies and working abroad, where his children could live in different countries and learn about other cultures.

But after he publicly claimed paternity of Hunter's child, Young said he knew the Edwards team had begun to do "opposition research" on him, trying to erode his reputation.

Young, who is testifying for prosecutors under an immunity agreement, was not on any official payroll at the time.

His wife, a part-time nurse, deposited hundreds of thousands of dollars into their private bank accounts - cheques written by Rachel "Bunny" Mellon, then forwarded to Bryan Huffman, a decorator who endorsed them and then sent them by FedEx to Young.

The scheme was to have Cheri Young additionally endorse the cheques, using her maiden name, and deposit them into the couple's account.

When asked by prosecutor David Harbach why he and his wife and others involved were "scared to death", Young stated he was worried whether it was legal, though he claimed Edwards had told him it was.

"We felt extremely uneasy about it, that it smelled and felt wrong," Young said. "We were all scared. This was a huge thing in the middle of a presidential race and we were scared to death."

Young, though, deposited hundreds of thousands of dollars in his personal account, and helped Hunter find housing in Chapel Hill after she complained that Edwards had cut it off with her and said she was considering going to the media with news of the affair.