DES MOINES, Iowa — Joe Biden’s campaign is working relentlessly to minimize his habitual verbal lapses, accusing the media of unfairly scrutinizing the Democratic front-runner while dismissing critics’ suggestions that he is unfit for the presidency.

As eyebrow-raising misstatements flow from the former vice president, his campaign is challenging the media’s credibility and painting rivals as equally prone to verbal blunders.

Biden, 76, has committed a string of mistakes in interviews, speeches, and town hall meetings since launching his third bid for the presidency four months ago.

During a recent swing through New Hampshire, Biden said he was in Vermont. Days earlier in Iowa, Biden said the assassinations of Robert F. Kennedy and Martin Luther King Jr. occurred in the late 1970s. He claimed he met with the survivors of a February 2018 mass shooting while he was still vice president. He left office in January 2017. The list goes on.

Through it all, Biden has maintained a lead in the race for the Democratic nomination in most public opinion polling, nationally and in key early primary states, buoyed by the relationship he developed with voters during his tenure as Barack Obama’s vice president. Biden has even led President Trump, 73, in most hypothetical matchups, both nationally and in critical 2020 battlegrounds. There are signs of vulnerability, however, with one national poll this week putting Biden third in a three-way statistical tie with Elizabeth Warren and Bernie Sanders.

In interviews the Washington Examiner conducted with voters likely to participate in the Democratic caucuses in Iowa, there were voters who were unsettled about Biden’s age. The veteran politician, a senator representing Delaware for 36 years before becoming vice president, had been known for his baritone voice, quick wit, and high-octane presence. When he entered the Senate in 1973, he was the youngest man there, constitutionally eligible to take his seat less than two months earlier, when he turned 30.

Now, some Democrats who think of Biden affectionately and might back him for the nomination are worried he might be slowing down.

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Some fret he might be stymied by Trump, just three years younger but a relentless and asymmetrical campaigner. Others are anxious about his ability to handle the rigors of the presidency. If Biden won, he would be 78 on Inauguration Day in 2021, supplanting Trump as the oldest to ever take the oath of office for his first term.

“I like him a lot. I’m concerned about his age,” said Cindy Schuman, a Democrat who has not ruled out caucusing for Biden. “I’m just concerned about his energy.” Schuman’s 66-year-old husband Jon, a CPA, has similar concerns "as it relates to energy to do the job, not [to] beat Trump, because Trump’s just as old and probably in worse shape.”

For many Biden-inclined voters verbal flubs were not a problem, at least not yet. “Why do you keep asking about Biden’s gaffes when we have put up with three years of Trump’s absolute nonsense?” said Virginia Petersen, 80, an undecided Democrat who showed up to see the former vice president at a campaign rally near Des Moines.

Andrew Bates, Biden’s rapid-response director, pushed back aggressively at coverage of Biden musing about Obama's assassination, tweeting: “The crowd didn’t even react because they understood his point. This click-chasing is sickening.”

A Vanity Fair article, which was well-sourced within the Biden campaign, referred to news coverage as "Joe Biden outrage porn" and quoted former Fox News campaign correspondent Carl Cameron, now helming a liberal website, saying: "The idea that Joe Biden has loose lips is as old as Biden himself.

“The problem for the press is that Trump says so much more stuff, all the time, and the ratio is just beyond description. He makes what we used to cover as gaffes look meaningless. So are we really going to have a gaffe-fest over Joe Biden?”

Biden has acknowledged that his age is an issue. In a brief interview with reporters after a campaign rally in central Iowa during which Biden spoke extemporaneously for more than 60 minutes and then stuck around to take selfies with voters for another hour, he said voters will have to observe and decide for themselves.

“It’s a legitimate thing to [be] concerned about my age, just like it was legitimate to discern when I was 29 whether I had the judgment to be a United States senator. I think it’s totally legitimate,” Biden said. “The only thing I can say is watch — watch. Check my energy level, determine whether I know what I’m talking about, make a judgment. That’s totally appropriate.”

Asked for comment, a Biden spokesman referred the Washington Examiner to an interview communications director Kate Bedingfield gave to MSNBC.

“I think the press has to be more careful about applying an unfair standard to Joe Biden than they’re applying to other candidates,” she said. "He’s always speaking from his heart. And sure, that means sometimes he’s going to misstate a couple of things. But frankly, so does every other candidate.”