Twelve Democratic presidential candidates squared off at a debate on Tuesday night in Westerville, Ohio, where Sen. Elizabeth Warren (D-Mass.) came under fierce attack, underscoring her rise to the top of the pack in the race for the nomination.

Here are the candidates who stood out during the debate.

South Bend, Ind., Mayor Pete Buttigieg

Buttigieg had a strong night and might have emerged as the winner of the debate.

The performance is well-timed for Buttigieg, who burst out of the gate but has stagnated in recent months.

Recent polls of Iowa show that he's getting a second look from voters, and Tuesday night's debate could give him a burst of momentum heading into the final months before the caucuses.

Buttigieg went aggressively after Sen. Elizabeth Warren (D-Mass.), accusing her of equivocating on the central question of whether taxes would have to be raised on the middle class to pay for her "Medicare for All" plan.

"Your signature, senator, is to have a plan for everything, except this," Buttigeig said.

The South Bend mayor had set himself on a collision course with Warren in recent weeks, taking positions to establish himself as a centrist who is not afraid to take on the progressive wing of the party.

Late in the debate, Buttigieg pivoted off of a Medicare for All squabble to accuse Warren of promoting "infinite partisan combat" and to criticize former Vice President Joe Biden for believing that Washington can return to normal after President Trump leaves office.

Buttigieg also memorably clashed with Rep. Tulsi Gabbard (D-Hawaii) over U.S. involvement in the Middle East, showcasing his foreign policy chops in a tense argument between two military veterans.

Sen. Elizabeth Warren (D-Mass.)

Sen. Elizabeth Warren (D-Mass.) faced a barrage of attacks from several of her rivals over some of the most defining issues of her presidential campaign. And she came out largely unscathed.

Whether it was former Rep. Beto O'Rourke's (Texas) accusation that she appeared "more focused on being punitive" than on healing the country's divisions or Sen. Amy Klobuchar's (D-Minn.) insistence that she was being misleading about the costs of a Medicare for All health care system, Warren stayed on message.

Democrats "succeed when we dream big and fight hard, not when we dream small and quit before we get started," she argued. And she swiftly pushed back at O'Rourke's accusation, dismissing "the notion that anyone thinks I'm punitive."

Indeed, her performance in the debate showcased some lingering challenges for Warren. She will almost certainly continue to face questions about whether she would raise taxes on the middle class to pay for a Medicare for All-type system. And the party's moderate wing will likely stoke skepticism about the practicality of her policy prescriptions.

But by the end of the night on Tuesday, Warren had showed that she was capable of standing up to attacks as a newfound front-runner in the Democratic nominating contest. What's more, the barrage of criticism suggests that Warren has steadily supplanted Sen. Bernie Sanders (I-Vt.) as the leading progressive in the primary field.

Tech entrepreneur Andrew Yang

For a candidate who was once seen as a longer-than-long shot for the Democratic nomination, former tech executive Andrew Yang scored a handful of wins on Tuesday night.

He shared quite a bit of screen time with Warren, engaging in an exchange over the impact of automation on American workers and economic anxieties. (Yang has warned that automation, not trade policy, is the primary culprit in the decline of manufacturing and other jobs in the U.S.).

And his Freedom Dividend proposal, a form of universal basic income (UBI) that calls for giving every American over the age of 18 a $1,000-per-month stipend, got nods from some other candidates on stage.

Former Housing and Urban Development Secretary Julián Castro said he was "willing to pilot something like UBI and see how that would work." And Rep. Tulsi Gabbard (D-Hawaii) suggested that she would consider a similar program if elected president.

That Yang's signature issues got so much attention in the debate suggests that, even if he's not a front-runner, his presence in the Democratic primary field is having an effect.

Sen. Amy Klobuchar (D-Minn.)

Klobuchar has at times struggled to stand out in the crowded field of big personalities, but on Tuesday night she left a mark with a string of surprise attacks against Warren.

On Medicare for All, Klobuchar told Warren that "at least Bernie is being honest" about how he'd pay for his plan.

"I'm tired of being told this is a Republican talking point," she said. "You're making Republican talking points right now in this room."

Later, Klobuchar ripped Warren for accusing the other contenders of seeking to protect billionaires.

"I want to give a reality check here to Elizabeth. No one on this stage wants to protect billionaires. Not even the billionaire [candidate Tom Steyer] wants to protect billionaires," Klobuchar said.

"Simply because you have different ideas doesn't mean you're fighting for regular people," she added.

The Minnesota Democrat has met the fundraising requirement for the November debate but still needs to meet the polling threshold to qualify. Tuesday night might be a step in that direction.

Former Vice President Joe Biden

The longtime front-runner was not a winner or a loser on Tuesday night, largely melting into the background of a debate that centered around Warren.

That might not be a bad place for Biden to be, considering his poll numbers dipped after previous debates in which he was the focus of attacks.

Biden's standout moment on Tuesday came when he blasted Trump's foreign policy.

"We have an erratic, crazy president who knows not a damn thing about foreign policy and operates out of fear," Biden said.

But at other times, it seemed that Biden flubbed his remarks.

Biden is holding strong in the polls despite Warren's momentum, and it's unlikely that Tuesday night's debate will change that.

Sen. Bernie Sanders (I-Vt.)

Two weeks after suffering a heart attack that raised new questions about his health and age, Sanders needed a debate performance that showcased his vigor and vitality.

For the most part, he appeared to rise to the challenge.

He got to riff on some of his core talking points, at one point even getting asked a question about whether billionaires should exist. (He responded with a condemnation of the amount of wealth controlled by the richest Americans, calling it "a moral and economic outrage").

And at another point, he reassured the audience that he was "healthy" and "feeling great," prompting loud applause, and vowed to demonstrate his vitality through his work on the campaign trail.

"We are going to be mounting a vigorous campaign all over this country," he said. "That is how I think I can reassure the American people."

But Sanders was also uncharacteristically quiet at times, registering noticeably less speaking time than his two top-tier rivals, Warren and Biden.

His best moment of the night came after the debate, when he landed endorsements from Reps. Alexandria Ocasio-Cortez (D-N.Y.), Ilhan Omar (D-Minn.) and Rashida Tlaib (D-Mich.). Support from members of the "squad" will give his campaign a much-needed shot in the arm.

Rep. Tulsi Gabbard (D-Hawaii)

It was a strange week for Gabbard in the run-up to the debate.

There is enormous online interest in the Hawaii Democrat, who has angered many in her own party for accusing Democrats of being complicit in "endless regime change wars" and alleging that the Democratic National Committee is "rigging" the primary against outsider candidates, such as herself.

A New York Times story that ran over the weekend - the paper co-hosted Tuesday night's debate - detailed support for Gabbard on the far right and insinuated that Russia is actively promoting her campaign.

Gabbard accused The New York Times and CNN - a CNN panelist questioned Gabbard's loyalty to the U.S. on the air earlier in the day - of "smearing veterans such as myself."

And she had a strong moment where she accused "both parties and the mainstream media" of "championing and cheerleading for regime change war."

However, it's unclear whether there's a big enough cross-section of Democrats to propel her into the next debate, particularly in a field that is flush with outsiders, including Yang and Sanders.