Bill Clinton addresses students on May 2, 2015 during an Equity Bank and Master Card sponsored Wings-to-Fly Secondary school scholarship program in Nairobi.National Journal

Former President Bill Clinton continues to be Hillary Clinton's greatest defender on the campaign trail.

As allegations swirl that the Clintons' foundation accepted cash from countries that had a specific interest in making the State Department happy while Hillary Clinton was secretary of State, Bill Clinton says that there is "no doubt" in his mind that the foundation had ever "done anything knowingly inappropriate in terms of taking money to influence any kind of American government policy."

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"That just hasn't happened," Bill Clinton said during an interview with NBC that aired in part Monday morning.

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For weeks, Hillary Clinton's campaign has been interrupted with allegations from news reports and a new book, Clinton Cash: The Untold Story of How and Why Foreign Governments and Businesses Helped Make Bill and Hillary Rich, that foreign governments donated to the Clinton Global Initiative in hopes of influencing the secretary of State. From a trade deal to the Keystone XL pipeline, Clinton Cash author Peter Schweizer argues that many of the foundation's donors had an interest in getting on Clinton's good side.

The book also zeroes in on Bill Clinton's robust speech-giving career, a cornerstone of the couple's income. According to the book, Bill Clinton made more than $13 million giving speeches in 2011. He delivered several in foreign countries and was paid while Hillary Clinton was serving as secretary of State.

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"It's the most independence I can get," Clinton said of his speech-giving. "If I had a business relationship with somebody, they'd have a target on their back from the day they did business with me until the end," Clinton said. "I work hard on this, I spend a couple hours a day just doing the research. People like hearing me speak. ... And I have turned down a lot of them. If I think there's something wrong with it, I don't take it. And I do disclose who gave them to me so people can make up their own minds."

During his interview with NBC, Bill Clinton defended his orating as necessary for his family.

"I gotta pay our bills," Clinton said.

He also was not sure he would step down from the foundation if his wife becomes president.

"Well, I'll decide; if it's the right thing to do, I will," Clinton said.

When asked what would spur him to step down, he said, "I might if I were asked to do something in the public interest that I had an obligation to do."

Correction: An earlier version of this story misstated what Bill Clinton said he may not do if his wife becomes president. He said he'd consider stepping down from the Clinton Foundation.

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