Presumptive Democratic vice presidential candidate Kamala Harris does not appear to have “any core convictions,” former House Oversight Committee Chair Trey Gowdy told “Outnumbered Overtime” Thursday.

“The American people will allow you to change your mind,” Gowdy told host Harris Faulkner. “If you change your mind 20 years ago and you can explain when and why, that’s one thing. But Harris, six months ago, she thought she would make a better president than Joe Biden."

Gowdy, a former state and federal prosecutor in South Carolina, further noted that though Harris claims to want police reform, she neglected to work with Sen. Tim Scott, R-S.C., on his legislative efforts to bring about change.

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“It just instructs this notion that she doesn’t have any core convictions aside from her personal ambition," Gowdy said. “She had it sitting across the table from her … and she stood up and said, 'I’m not willing to negotiate,' and she wouldn’t make an amendment.

"So, it feeds the narrative of 'Can we really rely on you now? You say you’ve changed your mind, what’s to guarantee us you’re not going to change it again?"

Gowdy went on to say that Harris, who was officially announced as Biden's running mate Tuesday, has switched her stances on multiple issues throughout her time in public life, beginning as a local prosecutor in the early 2000s.

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Those positions are now back in the spotlight, as the Trump campaign tries to tag the senator as "phony" and the newly named Democratic ticket prepares to present a united and consistent message going into next week's national convention.

Harris' changes of heart cover issues like whether the government should abolish private health insurance, whether recreational marijuana should be legalized and more. Such switches have invited criticism in the past from both the left and the right -- with Republicans labeling her as radical and members of the more progressive wing of the Democratic Party accusing her of not being liberal enough.

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Gowdy said Harris’ fickleness on social and political issues “feeds the narrative that her only core conviction is personal ambition.”

“Six months ago, it would take the Stanford linguistics department to figure out her health care position because nobody could understand it," he said. "Six months ago, she believed [Kavanaugh accuser] Dr. Christine Blasey Ford before she ever opened her mouth. Does she also believe Biden’s accusers?”

Fox News' Paul SteinhauserMadeleine Rivera, and Allie Raffa contributed to this report.