Bernie Sanders on why some should vote for Hi...

Sen. Bernie Sanders is casting Hillary Clinton as a flip-flopper on a range of key issues, heating up the race between the two presidential candidates.

In an interview on Charlie Rose Monday evening, the Vermont independent accused the Democratic frontrunner of flip-flopping on the international trade deal, the Keystone XL pipeline and on Wall Street regulations.

"There are real differences between Hillary Clinton and myself. I have been extremely consistent on my views for many, many years," Sanders told Rose.

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Sanders recalled that Clinton previously described the Trans-Pacific Partnership as the "gold standard," but said he's glad she now opposes it "years after I came out against it."

On the Keystone pipeline, Sanders said he opposed its construction from the "very, very beginning."

"She came around, I'm glad she finally came around," Sanders said about Clinton. "Now she's in opposition to the Keystone pipeline."

Sanders also said he led the opposition to the deregulation of Wall Street.

"I'm glad that over a period of time, Hillary Clinton has come out with some ideas about how you deal with Wall Street, but frankly, they don't go as far as they should," he said.

Both candidates have been trading barbs over the last few days about their records.

At several events, Clinton has said she was told to stop "shouting about gun violence," a reference to something Sanders had said during the Democratic debate, that "all the shouting in the world" won't "keep guns out of the hands of people who should not have those guns."

"Well, first of all, I'm not shouting. It's just when women talk, some people think we're shouting," she said.

Sanders rejected the notion that it was a sexist attack against Clinton.

Clinton has been doing well in several polls since her performance at the first Democratic debate earlier this month and at last Thursday's 11-hour Benghazi hearing.

A CBS News Battleground Tracker poll found 46 percent of likely Democratic caucus voters in Iowa support Clinton while 43 percent back Sanders.