Tonight’s Democratic Debate in Nevada: When It Is and What to Watch For

LAS VEGAS — There are two big questions for Mr. Sanders when he takes the debate stage: Will he be a target for attack? And will he attack Mr. Bloomberg?

Rivals challenged Mr. Sanders at times in the last debate, before the New Hampshire primary, but he emerged relatively unscathed. Now he is a front-runner, and front-runners have typically come under steady criticism in debates. After Mr. Sanders’s tie in Iowa and victory in New Hampshire, will any of his opponents finally go after him in a meaningful way?

At the same time, the arrival of Mr. Bloomberg onstage gives Mr. Sanders a prime opportunity to attack a billionaire candidate who represents much of what the Vermont senator despises. Will he play offense?

Mr. Sanders already appears primed for a strong performance in the Nevada caucuses on Saturday. For Sanders-watchers, the most interesting aspect of tonight’s debate is probably whether a man who rarely changes his message will do just that, and what effect it may have.

Ms. Warren has largely avoided attacking opponents, in debates and on the trail. As she seeks to jolt her stalled candidacy after a disappointing finish in New Hampshire, however, several signs point to this debate in Nevada as the moment that Ms. Warren will go on a sustained offensive.

The clearest one was on Tuesday when Ms. Warren called Mr. Bloomberg an “egomaniac” on Twitter and challenged her opponents to hold his feet to the fire. In another Twitter post, Ms. Warren said Mr. Bloomberg “approved and oversaw a program that surveilled and tracked Muslim communities in mosques, restaurants, and even college campuses — leaving permanent damage.”

If Ms. Warren carries out these attacks onstage, it will most likely provide her supporters with the moment they have been waiting for in recent months.

After the last debate in New Hampshire, when Ms. Warren did not interject into the conversation like many of her opponents did, some supporters expressed exasperation with an approach that could be relentlessly unflinching. Even Ms. Warren said after the debate that she wished she had jumped in more.

“I just didn’t say enough, didn’t fight hard enough, didn’t tell you how bad I want this and how good we could make it if we just come together,” she said.

She finished in fourth place days later in the New Hampshire primary.

For months, Mr. Buttigieg’s campaign was built around the idea that strong finishes in Iowa and New Hampshire would make him the inheritor of the Democratic Party’s Obama coalition.

But that calculation didn’t count on a billionaire candidate, Mr. Bloomberg, targeting Super Tuesday states in March and spending many times more on television advertising than Mr. Buttigieg could ever hope to raise from donors excited about his post-Iowa momentum.

While Mr. Sanders and Ms. Warren have sounded far more aggrieved about Mr. Bloomberg’s recent polling rise and his past statements about housing discrimination and stop-and-frisk police tactics, Mr. Bloomberg presents a far graver threat to Mr. Buttigieg than he does to their more liberal rivals.

Mr. Bloomberg can also deflect Mr. Buttigieg’s core argument: that it will take a mayor from outside Washington to galvanize an American majority to defeat President Trump. Mr. Bloomberg would fit that profile, too.

Mr. Buttigieg, who has struggled to appeal to black voters, may have difficulty attacking Mr. Bloomberg on his past statements about housing and policing, given his own difficulties on those fronts in South Bend, Ind.

Time and again, Mr. Buttigieg has proved himself to be a highly competent debater, able to land precise blows on his opponents while deflecting and counterattacking their shots at him. Trying to disqualify Mr. Bloomberg in the eyes of voters in Super Tuesday states, where some early voting is already underway, may be his most difficult task yet.

A strong debate performance close to an Election Day can make a meaningful difference for a campaign’s momentum — just ask Ms. Klobuchar, who received a post-debate surge in support right before the New Hampshire primary, and landed a surprise third-place finish there.

Mr. Biden, the onetime national front-runner who came in fourth place in Iowa and fifth in New Hampshire, could really use a substantial surge right now.

Is there anything he can do to stand out onstage Wednesday night?

He has previewed a range of arguments against his opponents, from alluding to Mr. Sanders’s record on gun control, to swiping at Mr. Bloomberg’s background as a former Republican. But Mr. Biden is often hesitant to draw sharp contrasts with rivals onstage when they are shoulder-to-shoulder. And throughout the campaign, he has had a number of disastrous debate moments — never mind achieving the kind of race-changing, breakout performance he needs now, in a state where his campaign believes he must finish in at least second place.

Mr. Biden is at his best, and his most comfortable, when engaging one-on-one with voters. Can he translate that appeal onstage in a memorable — and effective — way?

This story will be updated throughout the day with reporting and analysis focused on Ms. Klobuchar, Mr. Bloomberg and political news in Nevada.