"She's very calm when she's on the line and when I was on the line I was always calm, But when she's in the line of fire I get nervous. I think it's a, you know, it's a husband-wife thing."
The former president also said he will not play a direct role in her presidential campaign, but will work to raise money in New York.
"I can do a lot of New York fundraising because they'll take me here, and it saves her time when she can be in states she needs to be to get votes in the primary states," he said.
But the former president said he also discusses policies with his wife and will point out if an issue is being "neglected."
"I talk to her about her energy policy, talk to her about her healthcare policy, try to work out some of the complicated issues," he said. "Or if there's some element being neglected I'll say that."
In the wide ranging interview that aired Wednesday night on CNN's Anderson Cooper 360, Clinton also said he "takes it as a compliment" when GOP presidential candidates criticize his wife.
"I take it as a compliment because I believe they tried to dump on her and none of it stuck and therefore they'd like it if she didn't win."
The former president also said he is not surprised Illinois Sen. Barack Obama, Sen. Clinton's chief rival for the Democratic nomination, is fairing so well in the national polls.
"He's an attractive, compelling, charismatic guy who has not been in politics very long, therefore has not had the time to pick up enemies you pick up, or at least opposition, if you stay around and are in the fray and fighting to do things," the former president said.