One day after being overshadowed by Sen. Elizabeth Warren at the Democrats’ latest debate, Joe Biden repeatedly criticized the progressive senator from Massachusetts, whose status has risen in recent months, making her a presidential primary front-runner alongside the former vice president.

In Columbus, Ohio, Biden questioned Warren’s honesty and pushed back against the media’s labeling of Warren as a "co-front-runner."

“I haven’t seen any polling showing that nationally, on average, that anybody else is a front-runner,” Biden said. “You guys keep talking about that.”

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Biden did acknowledge, in referencing the latest polls, that “Warren has done very well. She’s moved.”

The former vice president was the unrivaled leader of the pack in the 2020 nomination race even before he declared his candidacy in late April. But Warren, gaining stature in a field that once had some two dozen presidential hopefuls, has surged; in many of the most recent national, early-primary-state and caucus-state surveys, she’s virtually tied Biden for the top spot.

Warren’s new status was clearly on display at Tuesday night’s fourth-round nomination debate, when she came under attack from many of her rivals on the stage. Biden, who was the recipient of most of the incoming fire during the first three rounds of debates, was at times absent from the action.

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Still, Biden downplayed suggestions that he’s been eclipsed by Warren, saying on the day after the debate that “it's kind of about time other people get questioned.”

But Warren's chief campaign strategist, Joe Rospars, pointing to the attention Warren received at the debate and to new fundraising reports that potentially hint at some trouble for Biden – tweeted on Wednesday that “it’s rare that we get as much real information in one day to clarify the state of the Democratic primary as we did yesterday.”

Near the top of Tuesday’s debate, two primary rivals -- South Bend, Ind., Mayor Pete Buttigieg and Sen. Amy Klobuchar of Minnesota -- forcefully took aim at Warren for not directly answering if she’d raise taxes on middle-class Americans to pay for her push to implement a government-run “Medicare-for-all” health care system.

On that score, Biden had this to say on Wednesday: “It’s fascinating that the person who has a plan for everything has no plan for the single most consequential thing in this election in the minds of the American people, across the board. And you know, credibility matters. It matters.”

"She’s going to have to tell the truth, or a question will be raised about whether she’s going to be candid and honest with the American people,” Biden said. “I don’t want to pick on Elizabeth Warren, but this is ridiculous. Absolutely ridiculous.”

Biden, who opposes the Medicare-for-all plan long championed by more progressive rivals like Warren and Sen. Bernie Sanders of Vermont instead supports strengthening the Affordable Care Act with a public option.

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“The last thing the Democrats should be doing is playing (President) Trump’s game and trying to con the American people to think this is easy,"Biden said. “There’s nothing easy about it. If you’re going to do it, tell us how you’re going to do it. It’s called truth in speaking.”

Warren’s campaign told Fox News that the senator is “reviewing the revenue options suggested by the 2016 Bernie [Sanders] campaign along with other revenue options.”

Warren further emphasized at the debate that “I will not sign a bill into law that does not cut costs for middle-class families.”

Beyond health care, Biden criticized Warren for saying during the debate that “I think that we [the United States] ought to get out of the Middle East.”

Warren – who sits on the Senate Armed Services Committee – appeared to suggest an end to the decades-old U.S. military presence in the volatile Mideast. Her comments came during a discussion of President Trump’s heavily criticized move to pull U.S. troops out of northeastern Syria.

While Warren has long called for reducing America’s military presence overseas, her campaign said after the debate that the candidate was talking only about combat troops.

“Senator Warren was referencing combat troops, not those stationed in the Middle East in non-combat roles. She believes we need to end the endless wars. That means working to responsibly remove U.S. troops from combat in the Middle East, and using diplomacy to work with allies and partners to end conflicts and suffering in the region,” the campaign said in a statement.

Biden, on Wednesday, said he “frankly was surprised” by Warren’s comments.

The former vice president – who repeatedly touts his foreign policy chops – added that “I had never heard any say, with any serious background on foreign policy, that we pull all troops out of the Middle East. … I’m not sure exactly what she meant by it.”

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“If she meant pulling our fleet out of the eastern Mediterranean or the Persian Gulf, I think it would be an absolute disaster for American security and American foreign policy.”

Biden repeated his criticism – without naming Warren – later Wednesday when he delivered a foreign policy address in Iowa.

Fox News' Tara Prindiville and Allie Raffa contributed to this report.