Sen. Claire McCaskill Claire Conner McCaskillMomentum growing among Republicans for Supreme Court vote before Election Day Democratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally MORE (D-Mo.) on Thursday took aim at MSNBC’s “Morning Joe,” asserting the show is treating Hillary Clinton unfairly.

“Everybody evolves on positions,” McCaskill said of Clinton during a testy interview with hosts Joe Scarborough Charles (Joe) Joseph ScarboroughScarborough calls on Cuomo to walk back statement he made about Trump: 'Out of bounds' Mika Brzezinski: 'Super grossed out' by Trump speech attendees 'who put their lives at risk' Democrats tear into Trump's 'deep state' tweet: His 'lies and recklessness' have 'killed people' MORE and Mika Brzezinski.

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“I’ve been listening to you guys this morning and I think some of it has been unfair and not balanced,” McCaskill said of the show's coverage of Clinton’s position on the Trans-Pacific Partnership (TPP).

“I really don’t think that this is an indication that she is somehow unprincipled or weak,” she added. "I think that’s totally wrong.”

Clinton, the front-runner for the presidential Democratic nomination, broke with President Obama late Wednesday by coming out against his Pacific Rim trade deal, which was finalized this week after years of difficult negotiations.

As secretary of State, Clinton had praised aspects of the emerging agreement, leading some to accuse her of reversing her position.

“What I know about it, as of today I’m not in favor of what I’ve learned about it,” Clinton told host Judy Woodruff on PBS’s “NewsHour.”

“I appreciate the hard work that President Obama and his team put into this process and recognize the strides they have made,” she added. "But the bar here is very high, and based on what I have seen, I don’t believe this agreement has met it.”

McCaskill said White House hopefuls from both political parties have shifted on the issues during the 2016 race.

“You look at [Sen.] Marco Rubio Marco Antonio RubioOvernight Defense: Pentagon redirects pandemic funding to defense contractors | US planning for full Afghanistan withdrawal by May | Anti-Trump GOP group puts ads in military papers Democrats step up hardball tactics as Supreme Court fight heats up Press: Notorious RBG vs Notorious GOP MORE [R-Fla.] and you look at [former Gov.] Jeb Bush [R-Fla.] and the changes in their position and how they twist and distort themselves to appeal to the same people who want to elect [GOP presidential front-runner] Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE president, it really is something to see,” she said, citing the pair’s morphing immigration positions.

“I’m glad that Bernie has evolved on guns,” McCaskill said, citing Sen. Bernie Sanders Bernie SandersButtigieg stands in as Pence for Harris's debate practice Bernie Sanders warns of 'nightmare scenario' if Trump refuses election results Harris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda MORE (I-Vt.), Clinton’s closest competition for the party's 2016 coronation. "He is now four-square with us on what we need to do, but Bernie is someone who voted against the Brady Bill.”

“I just don’t hear enough talk about that,” she added.

McCaskill added on Thursday that she is undecided about the TPP herself.

“She and I may disagree with it, ultimately,” McCaskill said. "In fairness to Hillary Clinton, she voted for some trade deals when she was in Congress, and she voted against others.”