Former Maryland Gov. Martin O'Malley went after Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE on Monday, suggesting the Democratic presidential front-runner has been consistent on only one thing: her support of big banks.

"Hillary Clinton has changed her position on virtually every defining issue in this race except for one — and that's to protect the big banks on Wall Street and go about with business as usual," the presidential candidate said on MSNBC's "Morning Joe."

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"I don't think that's what the people of our country are looking for. I have the independence; I have the backbone, to stand up for what our nation needs. That's what people are going to see now that it's down to a three-person race," he added.

O'Malley has previously noted that he has long opposed the Trans-Pacific Partnership (TPP), something Clinton voiced her position on earlier this month, as well as the Keystone XL Pipeline, which she also came out against recently.

O'Malley reiterated Monday his opposition to the TPP deal that leaders of the U.S. and 11 Pacific Rim nations recently negotiated.

"A weather vane shifts its positions in the wind. Effective leaders do not. I am clear about my principles, I know where I stand," he said.

O'Malley is one of three Democratic candidates now challenging Clinton, along with Sen. Bernie Sanders (I-Vt.) and Harvard Law School Professor Lawrence Lessig. All except Lessig, who is polling poorly and floating an independent bid, appeared at the Jefferson-Jackson Dinner in Iowa over the weekend.