Presidential candidate Cory Booker on Saturday urged fellow Democrats not to be distracted by vitriol directed at the party's candidates by the man whom they seek to replace.

Asked during a Charleston, South Carolina, town hall meeting how best to oppose President Donald Trump without running an overly negative campaign, the New Jersey senator said Democrats need to look inward and focus on issues important to many of them, such as health care and education.

"We have got to understand this is not about him, it's about us, and we should not be motivated by what we are against by what we are for as a country," Booker said.

As other Democratic hopefuls campaigned in early voting states, Sen. Bernie Sanders of Vermont made Brooklyn the official launch site of his second run for the White House, telling supporters that his campaign is tailor-made to defeat Trump. Sen. Elizabeth Warren of Massachusetts courted voters in Iowa while Sen. Sherrod Brown of Ohio visited South Carolina. Sen. Amy Klobuchar of Minnesota represented Democrats at the annual Gridiron Club dinner in Washington, an event where politicians traditionally poke fun at the press and other politicians.

Trump spoke to a gathering of conservatives in suburban Maryland, mocking Democrats for their framework to combat climate change and saying that House Democrats pushing to expand their investigations of him are "sick." He also predicted he would win re-election by a greater margin than his 2016 victory.

Highlights of Saturday's campaigning:

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CORY BOOKER

Taking questions from a diverse crowd, Booker urged the audience of activists, some waiving campaign signs, not to become complacent just because Democrats marked successes in the 2018 midterm elections. That drew a round of cheers from the Charleston crowd, where the party wrested the 1st District congressional seat from Republican control last fall for the first time in decades.

Booker also said that it's up to activism, not politics, to make substantive changes. He pointed to a longtime South Carolina politician, the late Sen. Strom Thurmond, a Democrat turned Republican who ran for president in 1948 as a Democratic segregationist.

"It wasn't Strom Thurmond who came to the Senate floor and said, 'Hey, wait a minute, hey guys -- it's time for those Negro people to have the right to vote,"' Booker said.

The senator also had sharp words for those who don't vote. "It is inexcusable that we have rates of voting in presidential elections at 40, 50, 60 per cent ... when so much is going to be hung in the balance in this election," he said.

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SHERROD BROWN

In the final swing of a political tour as he decides whether to enter the 2020 presidential race, Brown spent time this weekend in South Carolina. He stressed his commitment to higher wages and more robust health care and acknowledged the crucial role of the early-voting state.

At a Darlington County Democratic women's event, Brown said he values the important role that black women play in the primary process. South Carolina holds the first Southern voting, and its Democratic primary electorate is largely African-American.

"You can't be a Democrat in this country, especially in a state as diverse as Ohio -- you can't be a human being who's awake and not understand that black women are the heart of the Democratic Party," he said. "It's black women that drive this party. It's black women that get progressives like me elected."

Later Saturday, Brown was to speak at Dorchester County Democrats' oyster roast, an event that Booker was also scheduled to attend.

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BERNIE SANDERS

Sanders was in his birthplace of Brooklyn to call for Americans from all walks of life to join his effort for a political revolution, one he's been waging for four decades.

Calling Trump the most dangerous president in modern U.S. history, the Vermont senator said that his campaign is built to defeat Trump.

Sanders told supporters at a rally at Brooklyn College, which he once attended, that his campaign is saying "loudly and clearly that the underlying principles of our government will not be greed, hatred and lies. It will not be racism, sexism, xenophobia, homophobia and religious bigotry. That is going to end."

Sanders pledged to fight for "economic justice, social justice, racial justice and environmental justice."

He had begun his 2016 campaign in Vermont, which he has represented in the Senate for nearly two decades. But this time, as he tries to showcase more of his personal story, Sanders kicked off his 2020 bid in the New York City borough where he grew up as the son of a Jewish immigrant and lived in a rent-controlled apartment.

After Brooklyn, Sanders planned to travel to Selma, Alabama, where he will be among the politicians commemorating the anniversary of the 1965 clash known as "Bloody Sunday," when peaceful demonstrators were beaten back by Alabama state troopers as they attempted to cross the Edmund Pettus Bridge. A second campaign rally was set for Chicago, where he attended the University of Chicago and was involved in civil rights protests.

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ELIZABETH WARREN

During a campaign stop in Waterloo, Iowa, the Massachusetts senator emphasized the need for Democrats to focus on policies over personal attacks, and to remain united in order to win the 2020 presidential race.

"I'm not here to attack Democrats, I'm here to get our country back on track. I'm going to stay on the issues," she said, in response to a question from a voter about what she would do to avoid the primary becoming "a circular firing squad."

"This is our moment, and the need to get this right couldn't be more urgent," she added. "I'm going to support our Democratic nominee all the way."

Warren criticized Vice-President Mike Pence when asked by a reporter about former Vice-President Joe Biden's remarks earlier this week calling Pence a "decent man."

"I'm sorry, I followed Pence's history on LGBTQ Americans, and I don't think that is a decent position," she said.

Warren focused heavily on policy, but she refused to draw any contrasts between her own policy proposals and those offered by other candidates -- even when asked directly by a voter to clarify her health care policy. Warren said she supported Medicare for All, but that there were many ways to achieve universal coverage.

"We're working it through as Democrats. We're talking about it," she said.

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DONALD TRUMP

Trump aired his grievances and basked in the adoration of cheering conservatives after a trying week of tumult and setbacks, giving a stemwinder of a speech at the Conservative Political Action Conference that clocked in about two hours-plus and hardly left him winded or the audience disappointed.

Trump let loose against House Democrats broadening their investigations of him, predicted he would win re-election by a greater margin that his 2016 victory, taunted some of his potential White House challengers and sounded themes that are staples of his rallies.

The off-the-cuff remarks came at the end of the week that saw his nuclear summit with North Korea's leader collapse without an agreement, his former lawyer deliver congressional testimony about his character and business practices and Congress take action to nullify his emergency declaration to secure money for the border wall that lawmakers have denied him.

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Associated Press writers Juana Summers in New York City, Alexandra Jaffe in Waterloo, Iowa, and Kevin Freking in Oxon Hill, Maryland, contributed to this report.