LAS VEGAS — Former Vice President Joseph R. Biden Jr. took aim at Senator Bernie Sanders of Vermont on Saturday, calling on him to condemn the “vicious, malicious, misogynistic” rhetoric of some Sanders supporters and to do more to stamp it out.
The remarks came at a key time for both campaigns, as Mr. Biden tries to regain his footing after weak showings in the Iowa caucuses and New Hampshire primary — in which Mr. Sanders surged toward the front of the Democratic pack — and a week before next Saturday’s Nevada caucuses.
The zeal of Mr. Sanders’s online base has been both a source of strength and perpetual aggravation for his campaign, which has delicately balanced condemning bullying without diluting the force of his most fervent followers.
Mr. Biden’s comments on Saturday specifically seized on attacks that Sanders supporters had made against officials at the powerful Culinary Workers Union, Local 226, after that union had criticized Mr. Sanders’s health care plan.
“If any of my supporters did that, I’d disown them,” Mr. Biden said as part of an interview with “Meet the Press,” which will air Sunday on NBC. “To say ‘I disassociate’ is one thing. Find out who the hell they are, if any of them work for me. Fire them. Find out. See what’s going on.”
Asked about Mr. Biden’s comments, a spokesman for Mr. Sanders, Mike Casca, said that Mr. Sanders “continues to be unequivocal on the issue,” pointing to remarks the senator had made earlier in the week. “Anybody making personal attacks against anybody else in my name is not part of our movement,” Mr. Sanders had said. “And I’m not so sure, to be honest with you, that they are necessarily part of our movement. You understand, you know, the nature of the internet.”
Mr. Sanders went on an offensive of his own Saturday night. At a Clark County Democratic Party dinner at the Tropicana Las Vegas, Mr. Sanders spoke first among all the candidates and devoted a sizable portion of his remarks to attacking an opponent who was not present: Michael R. Bloomberg.
Mr. Sanders denounced “racist policies like stop-and-frisk,” a reference to the policing tactics under Mr. Bloomberg when he was mayor of New York City, which have been criticized for disproportionately affecting minorities and for which Mr. Bloomberg has apologized. Mr. Sanders also criticized Mr. Bloomberg as “a candidate who opposed modest proposals during Barack Obama’s presidency to raise taxes on the wealthy while advocating for cuts to Medicare and Social Security.”
He concluded: “The simple truth is that Mayor Bloomberg with all his money will not create the kind of excitement and energy we need to have the voter turnout we must have to defeat Donald Trump.”
The barbs came as early voting for Nevada’s Democratic caucuses began on Saturday, with most of the leading candidates rallying supporters amid lingering concerns about whether Nevada would be able to avoid a repeat of the caucus fiasco in Iowa.
As Mr. Sanders addressed a crowd in a high school cafeteria on Saturday morning, with a mariachi band taking the stage before he did, his supporters were sharply focused on the process as well as on Mr. Sanders and his opponents.
Numerous people expressed concern about the logistics of a caucus in which they want to deliver a speedy and unequivocal victory to their candidate.
“I went to a training last week, and there are lots of concerns among the campaign — ‘How’s it actually going to work?’” said Paul Kleemann, a precinct captain volunteer for the Sanders campaign who teaches high school guitar in Las Vegas. “We were supposed to use the same app as Iowa, but they scrapped that, and as of Wednesday, they hadn’t released how they were going to get the early caucus results to the precincts.” He added, “It’s a little frightening at this point.”
In Nevada, early voting is being held from Saturday through Tuesday in advance of next Saturday’s caucuses. At an early caucus site at the East Las Vegas Library, voters waited in a 40-minute line on Saturday morning. After presenting their IDs, they filled in paper ballots by order of their choices, up to a total of five, then deposited them in a slotted box. The state Democratic Party said that almost 12,000 people had participated in the early voting as of 5 p.m. Saturday.
The ballots will be shared with the caucus precincts corresponding to their residences. If their first choice is not viable in their home precinct, the next in line will be counted if that person reaches the 15 percent threshold.
“This is the first time we’ve done early voting, and we’ve got to get this right because all eyes are on Nevada,” Representative Dina Titus, Democrat of Nevada, said on Friday. “And if we do a good job, then maybe we get to be first instead of Iowa next time around.”
Still, the concerns about the process did not distract from the high stakes for the candidates.
The burst of campaigning in Nevada signaled a new phase in the primary race, after the Iowa caucuses on Feb. 3 and the New Hampshire primary this past Tuesday. The candidates have now plunged into a pivotal and chaotic portion of the calendar, with critical contests coming up in Nevada and South Carolina, and a slew of contests looming on Super Tuesday on March 3.
Mr. Sanders came into the weekend riding high, having emerged from New Hampshire with a victory in this past week’s primary, and he was one of several candidates who sought to rally supporters in the state on Saturday.
Mr. Biden, seeking to stabilize his campaign with a strong showing in Nevada., visited a barber school before making several other campaign stops.
Earlier, in an interview on Friday, Mr. Biden was pressed by the Univision anchor Jorge Ramos over the deportations that occurred during the Obama administration. “We took far too long to get it right,” Mr. Biden said. Asked about deportations of people without criminal records, Mr. Biden responded, “I think it was a big mistake.”
As she fights to build on momentum coming out of New Hampshire, Senator Amy Klobuchar of Minnesota began Saturday in the suburb of Henderson, speaking at a wedding event center tucked inside a strip mall. She said she had received more than $3 million in online donations since the New Hampshire primary.
Senator Elizabeth Warren of Massachusetts, seeking to reignite her sliding candidacy, tried to lean on her local ties in a town-hall-style event on Saturday, trumpeting her links to former Senator Harry Reid of Nevada and her connections to the labor movement that holds so much power in the state.
Ms. Warren also began airing a new television advertisement that invokes Mr. Reid as well as former President Barack Obama.
“When she talks, people listen,” the ad quotes Mr. Reid saying of Ms. Warren.
At the early caucus site at the East Las Vegas Library, much of the interest was directed toward someone not on the Nevada ballot.
Linda Vaganov, a Navy Reserves veteran who is on disability, said she voted for Ms. Klobuchar but really wanted Mr. Bloomberg to be the nominee.
She said Mr. Bloomberg had the money and street-fighting instincts to defeat President Trump. “I don’t see Biden as the street fighter that Bloomberg is,” she said. “When I saw Bloomberg’s tweets to Trump, I thought, this guy can get down and dirty and still look dignified.”
Mr. Reid, who appeared at the caucus site in a wheelchair, has not endorsed a Democrat in the race and generally praised all of the candidates he was asked about.
He said it was “way too early to count Joe Biden out” and shrugged off a question about whether Mr. Sanders would hurt down-ballot Democrats.
“Well they’ve been saying that about Bernie since long before he started running,” he said, adding, “All the polls show that if he becomes the nominee, he will beat Trump.”
Asked about Mr. Bloomberg, Mr. Reid said: “Mayor Bloomberg came to my home. I met him, of course, when I was the leader. I like him a lot.”
Jennifer Medina and Astead W. Herndon contributed reporting.