Des Moines, Iowa (CNN) Sen. Cory Booker has promised to run a relentlessly positive and unifying campaign, preaching love as an antidote to the nation's ills during his first trip to Iowa as a presidential candidate this weekend.

It's a message that sets him apart in a large and growing Democratic field: Booker isn't the only candidate talking about bringing a polarized nation together, but some of his rivals have tried to channel their party's anger at President Donald Trump. Whether Democratic voters think a candidate wrapped in a message of love has the mettle to beat Trump might be one the fundamental questions around Booker's campaign. As Booker conceded himself following his campaign launch, "Love ain't easy."

But it's a theme that has underpinned his political identity for many years, dating back to his time in Newark.

I'm "committed to running in a different way," he told the crowd in Mason City, where he made his first stop of the trip Friday in a church basement — advocating an approach less confrontational than conciliatory.

"This can't just be about an election," Booker said. "This has to be about a larger campaign for our country. ... I want to win the White House back, but it's not to beat Republicans. It's to unite Americans."

Booker's approach has elicited jeers from the White House, with counselor Kellyanne Conway recently likening his rhetoric to "a Hallmark card." At an event Saturday in Marshalltown, Iowa, Booker laughed off that characterization, saying of Conway, "I had a life's purpose far before she had an opinion."

"I'm not here to try to emulate the tactics of the President. I'm not trying to match him ugly comment for ugly comment, bashing for bashing," Booker elaborated during a sit-down with CNN. "I'm focusing on the people. That's what I've done in my life, and I've come through tough, tough political environments."

A central part of Booker's pitch is his time as mayor of Newark, and the political grit it took to get him there. After moving into Newark's inner city fresh from Yale Law School, Booker launched his career when he challenged and defeated a longtime incumbent on the City Council. He then took on the avatar of the Newark machine, Mayor Sharpe James, in a bloody political battle that Booker ultimately lost — a campaign chronicled in an Oscar-nominated documentary, "Street Fight."

"There's nobody in this race tougher than me," Booker told a crowd Saturday in Marshalltown, Iowa, pointing to that political crucible. "...I'm confident in my strength, and I'm confident in my toughness. ...Whatever (Trump) wants to throw at me, bring it, because I'm ready."

Even at this early stage in the campaign, roughly one year out from the Iowa caucuses and as Booker and other candidates are still introducing themselves to voters, that message is beginning to break through among Booker's prospective supporters.

"I think Cory Booker is a fighter," said Steven Juhl, who attended Booker's event in Mason City. "Look where he's at, look where he came from he came from, the projects in New Jersey."

But as much as Booker says he is ready for the attacks that are sure to come from the President, he doesn't plan to meet those attacks with his own.

"As a guy who was mayor and actually ran a city with a fire department, you can't really fight fire with fire," he told CNN. "That creates a whole lot more burning things down. I'm trying to say that we as a country, we need to rise up."

A CNN survey this week found the priority for Democrats in deciding which candidate to support is whether they have "a good chance of beating Donald Trump." However, that needn't necessarily translate to a fire-breathing campaign message, some Democrats say.

"The winning message is the one primary voters believe is authentically who you are," said Jesse Ferguson, a Democratic strategist who worked for Hillary Clinton's 2016 campaign. "So, if your career has been centered on bringing people together and creating a more hopeful and optimistic politics, then that's what you should run on, because anything else with be called out as BS."

It might also bode well for Booker that campaigns centered on love and national unity have a winning track record with Democratic presidential candidates, including Barack Obama in 2008 and Jimmy Carter in 1976. Booker has pointed to Carter as a model for his own message.

"There are a lot of primary voters who are angry and who want a change direction of the country," said Ferguson, "but that was true in 2008, and Democrats still wanted a hopeful and optimistic approach."

Iowa was the launching pad for Obama's successful 2008 campaign, and Booker's team hopes a message of love will again resonate with voters in the key caucus state. He is already generating intense interest: in Des Moines on Saturday, Booker's last of six stops in Iowa, an overflow crowd exceeded 500 people, according to the campaign's estimate.

On stage, Booker's voice was giving out after two grueling days of travel around the state. But he remained firm in his core message.

"I'm gonna get criticized, so I'm going to get ahead of it. They're going to say, 'Oh gosh, more candidates talking about love and hope, oh my God. How are you going to beat Donald Trump with that?'" Booker said.

"There are going to be different theories of how you fight in this election," Booker added. "Everybody's tough, I know there's a lot of great fighters there. But I've learned that when it comes to being tough, I never want people to think that in order to be tough you have to be mean, in order to be strong you have to be cruel. I want to campaign like I want to govern."