Concord, New Hampshire (CNN) Joe Biden made his way down the long corridor of the New Hampshire State House that his campaign lined with cheering voters, and he did it slowly.

It's not that he couldn't move faster, it's that he clearly didn't want to. Stopping and talking to people, especially young people there to greet him, is the essence of Biden. Aides joke that it often takes him longer than scheduled for him to get to events because he talks to everyone.

That was vividly on display here, where he was taking part in a Granite State rite of passage: filing for the first-in-the-nation primary here in person. Spending the day with Biden, as CNN did on Friday, was to watch him on the front lines of an increasingly heated two-front war as he seeks his party's presidential nomination in 2020: against his Democratic rivals and also President Donald Trump

Biden continues to face attacks from Trump and his allies over his son Hunter Biden's foreign business dealings. And the former vice president is engaged in an increasingly ugly back and forth with Massachusetts Sen. Elizabeth Warren over health care policy.

When asked if Trump's relentless attacks are helping, without hesitation, he said yes.

"They're helping me in every way," Biden tells us, arguing the basics: Democratic voters see that the President considers him a threat.

Biden also suggested that he doesn't want to fight with Warren but feels he has no choice after she suggested his arguments against her plan to fund "Medicare for All" meant he was running in the wrong presidential primary. He responded by calling her approach elitist , writing that they "reflect an angry unyielding viewpoint that has crept into our politics." On Friday, in an email to supporters, Warren embraced the angry label, writing, "I am angry and I own it," and said women have been told "over and over" that they are not allowed to be angry.

Biden told us attacking Warren, using a term some see as sexist, was "not anything that I did or was intended to do."

"I was responding to a comment she made," Biden said. "She said that anyone who disagreed with her and took her on, on her issue of Medicare for All, somehow either was a coward, wasn't willing to stand up and state what they thought. Somehow doing something -- I think the phrase was should be in a Republican primary. When we talk about Medicare for All, people talk about taking two years, five years, 10 years to get it done. That doesn't give any real reassurance to people out there," he explained.

When asked directly whether somebody who supports Medicare for All, a sweeping liberal proposal that would create a national health care system, can beat Donald Trump, Biden demurred.

"I'm not going to make that judgment," he told CNN.

Biden's sharpened attacks on Warren comes as a recent Monmouth University poll shows Warren catching Biden at the top of the field among Democrats nationally. She has also placed in the top tier in the most recent surveys of likely Democratic voters in Iowa and New Hampshire, while Biden has fallen behind the pack in some early state polls.

The rough reality for Biden, one his campaign started setting expectations about months ago, is that despite being a front-runner, he's not there alone and he very well could lose Iowa and New Hampshire.

If that happened, would his candidacy survive?

"I think I'm going to do better in both places than that," Biden insisted.

Pushed again on what would happen, Biden replied: "Not going to go there," he replied.

On the trail

For Biden, being greeted here in New Hampshire by throngs of people holding campaign signs and beating drums (props born out of one of Biden's greatest hits lines -- that he will beat Trump "like a drum") was a chance to show passion behind a candidacy that leans hard into the practical.

"Eight years of Donald Trump will forever and fundamentally change the character of this country, and that's why I am running," Biden declared at a rally outside on a blustery cold day.

Other candidates, especially his fellow leading contenders like Warren and Bernie Sanders, are selling a wholesale change in approach to governance. Biden is not. He is all about getting Trump out of the White House and says he's the best to do it.

Still, in an interview inside the State House gift shop, he insisted that his candidacy is about more than a pragmatic promise to beat Trump.

"You feel passion for your campaign?" we asked.

"I do, sure I do. Or I wouldn't be, look, the only reason I'm doing this is because we cannot, we cannot continue down the road of dividing this nation and walking away from the rest of the world," he replied, ticking off reasons he said the President has hurt America globally.

It's an understandable approach. Talking to voters who came to see him, many said flatly that the main reason they're considering supporting Biden is because he has the best chance of defeating the President, which anecdotally here, just as in polls of Democratic voters, matters more than anything to them in 2020.

On the stump, Biden's campaign clearly tries to weave in reminders of his experience, with opportunities to show how he has grown.

At a roundtable to discuss the Violence Against Women Act, which he helped write in the Senate, Biden goes deep into the history of how hard it was to convince his male colleagues to make changes that are taken for granted in 2019, like making it illegal for a man to rape his wife.

To show he has a grasp on modern day issues, he reminded the audience that men -- especially trans men -- are frequent victims of violence.

Events like this also allow for Biden to do what Biden does best: emote and empathize. After the event was over and the microphones turned off, he stayed in his seat talking intensely to a woman who told her own story of being a victim of violence.

Later, at a town hall in Franklin, New Hampshire, two of the questioners were children. One about climate change, and another about gun violence.

"How are you going to make schools more safe from mass shootings?" asked a 10-year-old boy who said his name was Jordan.

"Think about this. Those of you over 30. Could you ever imagine having asked that question?" responded with a question of his own from the audience.

"You talk about the soul of America. It's a sick soul we have when in fact we send our kids into school these days that duck and cover." he added.

Third time a charm?

The first time Biden ran for president was 1987. The world has changed a lot since then, and -- riding with him to an event -- he insists he has changed with it. This is Biden's third time running for president, which he admitted is tricky.

"The good news is the bad news. Everybody knows me. Everybody has an opinion. So it's harder to mislabel me or to say something about me that's not true. I have weaknesses. It's easier to talk about the weaknesses, but the generic point is that people know who I am," he said.

Familiarity and comfort drew voters we talked to see him, even though some said they're are not sold yet.

Ruth Kovacs and Terri Arangio were at the State House to see Biden wearing his campaign stickers and holding his signs.

But they told us they're still actively candidate shopping.

"Not 100%" Kovacs said about her support for Biden. "Personally, I like the middle of the roaders, not far left. I like Amy [Klobuchar], Pete Buttigieg and of course Joe Biden."

"I've always loved Joe Biden," added Arangio.

"He's a likable guy, he says what it is, sometimes he has his gaffes, but I think that's what makes Joe Joe."

We met several voters who said they came to see Biden in person, a privilege that Granite State voters hold dear, in order to see for themselves if the 76-year-old former vice president seems too old to be president.

Eric Swendsen came to the Franklin town hall with concerns about Biden's age, but told us he felt better after seeing him in action.

"I think he'll be fine. I think he'll be just fine," Swendsen said in his post-town hall assessment.

It is a topic we discussed with Biden during our car ride -- that anecdotally older voters who are his age tell us they can't imagine having the stamina to be president.

"What I tell them is, 'Watch me.' Oh God. The one thing that I've learned is, hopefully that age comes with experience, with experience comes with adjustment, and with adjustment comes some wisdom."