Hillary Clinton says she wasn't watching the Republican convention, but she heard about the chanting from the convention floor to "lock her up, lock her up," which was a response to the decision of the Justice Department not to charge her for mishandling classified information because she used a private email server while she was secretary of state.

Clinton, who appeared with her running mate, Virginia Gov. Tim Kaine, told CBS News' Scott Pelley that it just made her "sad" about what it said about the Republican campaign.

"I seem to be the only unifying-- theme that they had," she said. "There was no positive agenda. It was a very dark, divisive campaign." The negativity, "fear, bigotry, smears" saddened her, she said in the interview, which aired Sunday on "60 Minutes."

One of the issues that has been difficult for Clinton to shake is that of her private email server -- she promised it wouldn't be a mistake she'd make twice. Clinton reiterated that she set it up because "it was recommended that it would be convenient, and I thought it would be. It's turned out to be anything but." And she told Pelley, "I'll tell ya one thing, that is one lesson I have learned the hard way, and there will not be any such thing in the White House."

While "Crooked Hillary" may be the moniker that Donald Trump will use to refer to her through November, Clinton said she'll have no nickname for him in return, and she will instead "talk about what he's done," focusing on his business record, his insults of Judge Gonzalo Curiel, the judge in the Trump University lawsuits, his mocking of a New York Times reporter for his disability and his inflammatory language about Muslims and women.

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Clinton and Kaine granted their only joint interview this weekend to "60 Minutes," which was recorded a day after Clinton named Kaine as her running mate. She chose him, she said because above all else, she felt he was ready to be president. Asked by Pelley if he would be ready, Kaine said he would.

"I think I'm ready to lead. I-- I'm ready first to be a supportive vice president so that the presidency of Hillary Clinton is-- is a fantastic one," Kaine said. "But if something were to put that in my path, as much as any human being would be ready, I'd be ready."

Clinton also talked about the goals she cares most about, should she win the presidency -- "getting the economy working for everybody," defending and improving, addressing addiction problems, as well as systemic racism in the U.S., and improving gun safety.

Like President Obama, however, Clinton would also face challenges in Congress in getting her agenda enacted. But Clinton and Kaine were optimistic about their ability to work with Congress, in particular because they believe the GOP Senate will turn Democratic after November. Both also said they were eager to work with Republicans in Congress, in the vein of the work of then-House Budget Chairman Paul Ryan and then-Sen. Budget Chair Sen. Patty Murray, who succeeded in forging a compromise on a budget.