Sen. Cory Booker, D-N.J., officially launched his 2020 presidential campaign Friday, invoking a message of economic populism and racial justice along with a veiled swipe at President Donald Trump's leadership.

The 49-year-old former mayor of Newark, New Jersey, joined the fast-growing field of hopefuls vying for a White House run.

"People in America are losing faith that this nation will work for them, they're beginning to believe that too many folks are gonna get left out or left behind, they believe that forces that are tearing us apart are stronger than those that bond us together," he said during a news conference outside his Newark home. "I'm running for president because I want to address these issues."

Booker said his campaign will be about pushing Washington, as well as ordinary Americans, to overcome hostility and divisiveness, while expanding opportunity for all. In a video announcement earlier Friday morning, he said he was running because he believes "we can build a country where no one is forgotten, no one is left behind...where our criminal justice system keeps us safe, instead of shuffling more children into cages and coffins; where we see the faces of our leaders on television and feel pride, not shame."

Booker becomes the second African-American to enter the 2020 race, after Sen. Kamala Harris, D-Calif. His decision to announce his candidacy Feb. 1 — the first day of Black History Month — could be seen as a nod to the historic nature of his bid to become the nation's second black president.

In his news conference Friday, Booker defended his record as the mayor of Newark, a majority black city.

He pointed to his success at rescuing affordable housing for low-income residents and creating jobs, among other issues, as a microcosm of what his presidency could accomplish at the national level, and responded to a statement from the Republican National Committee that called him an "opportunist who left Newark ridden with crime and an 'emblem of poverty."

"This is what we have is people, for political purposes, not talking about what they're for but talking about what they're against. Newarkers, and I think people in cities all across America, are tired of people who are putting down our urban spaces and trying to make them into jokes," Booker said. "My time here in Newark was during the worst economy of my lifetime and we did things other people thought was impossible to do."

Booker stayed true to his campaign's message of limited mudslinging when asked if he believed Trump was a racist, saying he doesn't "know the heart of anybody." However, Booker said, the president has used "bigoted language" and emboldened white supremacists.

"I know there are a lot of people who profess the ideology of white supremacy that use his words. And I believe his failure to condemn bigotry and racism," he said. "I just want everybody to know I’m gonna run a race about not who I’m against or what I’m against, but who I’m for and what I'm for."

Trump knocked Booker in an interview with CBS News' "Face the Nation" moderator Margaret Brennan that's slated to air Sunday. "He's got no chance," Trump said of Booker in excerpts released Friday night. Asked why, the president said, "Because I know him. I don't think he has a chance."

Earlier, Booker kicked off his campaign by calling in to two radio shows with largely African-American audiences and doing an interview almost entirely in Spanish on Univision's morning show, Despierta América.

"Folks are feeling left out, folks are feeling left behind … I'm running for president to change that," Booker said on the nationally syndicated Tom Joyner Morning Show.

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He also spoke about mass incarceration and inequality, advocating for criminal justice, drug law reform and an end to marijuana "prohibition," while pushing a message of unity and inclusion.

"It's time for a more radical empathy in this country," he said on the show.

Booker was elected to the Senate in 2013 and has earned a reputation as one of the body's most outspoken members. His profile grew as he fiercely criticized Trump and his policies.

He made history in 2017 when, as a member of the Senate Judiciary Committee, he took a seat in front of the panel and testified against then-Sen. Jeff Sessions' nomination for attorney general. He was also part of the Democratic charge against Supreme Court nominee Brett Kavanaugh, and prompted controversy releasing a batch of documents about Trump's pick for the high court.

Despite his role as an adversary of the Trump administration, Booker also helped shepherd the White House's sweeping criminal justice reform bill through the Senate, which the president signed into law last year.

Booker's campaign said it plans to reject corporate donors, super PACs and contributions from federal lobbyists.

He plans to travel to the early states of Iowa and South Carolina next week and New Hampshire over President's Day weekend. Booker gave the keynote address at the Iowa Democratic Party's Fall Gala in October.

Booker appeared on ABC's "The View" in his first live television interview since announcing his run, with his mother and brother sitting in the audience. He stuck to a message of unifying America and billed himself as a problem-solver who can reach across the aisle.

"I've spent my entire career running at problems people said couldn't be solved," Booker said. "My conviction is that we can do impossible things when we come together."

He also said he expects some "sibling rivalry" in the Democratic primary, calling Harris and Sen. Kirsten Gillibrand, D-N.Y., "friends" and "sisters." But, he said, the primary shouldn't be about attacking each other.

“I don't want it to be defined by what we're against, but by what we're for. I don't want it to be defined by beating Republicans, but by uniting Americans."

However, at his news conference in Newark on Friday, Booker signaled he could break from some of the policies suggested by his 2020 competitors when he said he was against abolishing private health care. Harris, who supports Medicare for All, has said that she is for getting rid of private insurance.

He also defended his ties to Wall Street, by saying that he has always stood up for "people who have been hurt by bad actors."

Gillibrand welcomed him to the race, calling him one of her "closest friends."

"Congratulations and welcome to the race to one of my closest friends, @corybooker! I'll be cheering you on — just, you know, not TOO hard," she wrote, along with an old video of the pair ribbing each other.

Congratulations and welcome to the race to one of my closest friends, @corybooker! I'll be cheering you on—just, you know, not TOO hard. pic.twitter.com/zeWskppQpv — Kirsten Gillibrand (@SenGillibrand) February 1, 2019

Democratic Sen. Bob Menendez, Booker's colleague from New Jersey, was quick to endorse him.

"I can't think of anyone better to represent and unite the American people. Cory makes a great friend, and will make an even greater president," Menendez said Friday on Twitter. "I can't wait to support you on this journey—I'm all in!"

I can't think of anyone better to represent and unite the American people. Cory makes a great friend, and will make an even greater president.



I can't wait to support you on this journey—I'm all in! #Cory2020 - RM https://t.co/qgkubtxhXn — Menendez for NJ (@BobMenendezNJ) February 1, 2019

Booker also embraced the response to his announcement by interacting with fans and detractors on social media.

Thank you for this commitment. https://t.co/RWlEuoy0OS — Cory Booker (@CoryBooker) February 1, 2019

"Thank you for this commitment," he told one fan who vowed to support the candidate who wins the Democratic nomination for president.

One critic told the lawmaker he could not wait to see Trump "crush your soul," to which Booker shot back: "My soul belongs to God. I fear no man. And I believe that anyone's individual capacity to denigrate will never be as strong as our collective power to elevate."

In another tweet, the Hot Pockets official Twitter account told Booker, "don’t forget about us when you get elected" and attached an old photo of the lawmaker with the product.

Booker responded: "My dad used to say to me: 'Boy, don’t forget where you came from and the people who sacrificed to get you to where you are'."

My dad used to say to me: “Boy, don’t forget where you came from and the people who sacrificed to get you to where you are.” https://t.co/PqESzfPUYG — Cory Booker (@CoryBooker) February 1, 2019

CORRECTION (Feb. 1, 2019, 7:40 a.m.): A previous version of this article misstated Booker’s age. He is 49, not 43.