After Delaney said during his opening statement that Medicare for All was an “impossible promise that will turn off independent voters and get Trump reelected,” Sanders had a blunt response: “You’re wrong.”

The moderate candidates ― none of whom is on track to qualify for the third round of presidential debates in September ― hammered some of Warren’s and Sanders’ signature proposals as unrealistic and politically unwise, while Sanders and Warren argued they were necessary to fix the country’s problems and that the moderates were proposing insufficiently bold ideas. The debate seems unlikely to lead to a major shakeup in Democratic polling and lacked a clear breakout moment or candidate.

CNN’s moderators quickly set up clashes between Warren and Sanders and lower-tier moderates including former Maryland Rep. John Delaney, former Colorado Gov. John Hickenlooper, Montana Gov. Steve Bullock and Ohio Rep. Tim Ryan on contentious topics including immigration and “Medicare for All.”

DETROIT – An expected showdown between the race’s two leading progressive candidates instead quickly turned into a battle with Massachusetts Sen. Elizabeth Warren and Vermont Sen. Bernie Sanders facing a host of lesser-known moderate candidates desperate to continue their low-polling campaigns.

ASSOCIATED PRESS CNN’s moderators quickly set up clashes between Warren and Sanders and lower-tier moderates during Tuesday's Democratic presidential debate in Detroit.

To a certain extent, Delaney and other moderate candidates functioned as stand-ins for Vice President Joe Biden, the leading moderate candidate in the race, who will participate in Wednesday night’s debate. CNN’s moderators repeatedly returned to Delaney and Hickenlooper, asking them multiple times to criticize Warren and Sanders, who largely presented a united front against centrist critiques.

“They’re running on telling half the country that your health insurance is illegal,” Delaney said of Warren and Sanders, referring to their support for Sanders’ Medicare for All plan, which would outlaw private insurance ― a line often used by Republicans, but also by Democrats who oppose Medicare for All, including Delaney and Biden.

“Let’s be clear about this,” Warren responded, pointing to GOP support for repealing the Affordable Care Act. “We are the Democrats. We are not about trying to take health care away from anyone. That’s what the Republicans are trying to do. And we should stop using Republican talking points.”

Hickenlooper and the other moderates also critiqued Warren and Sanders as unelectable. The former Colorado governor ― who won elections twice in a swing state during GOP wave years ― said nominating Sanders would be the equivalent of political suicide.

“That is a disaster at the ballot box — you might as well FedEx the election to Donald Trump,” he said. Sanders retorted by noting he routinely tops Trump in public polling.

Bullock, meanwhile, warned that the party’s leftward shift on immigration this cycle ― especially the idea of decriminalizing the act of crossing the border without authorization ― would prove politically unpopular and provide Trump with another way to fire up his base before November 2020. Warren and other Democrats have noted the criminalization of border-crossing is how Trump legally justified family separation.

“We need to fix the crisis at the border, and a big part of how we do that is we do not play into Donald Trump’s hands. He wants to stir up the crisis at the border because that’s his overall message,” Warren said.

“But you are playing into Donald Trump’s hands,” Bullock responded. “The challenge isn’t that it’s a criminal offense to cross the border, the challenge is that Donald Trump is president and using this to rip families apart. A sane immigration system means a sane leader.”

Three candidates who stand between the progressives and moderates ideologically and in the polls ― Minnesota Sen. Amy Klobuchar, South Bend, Indiana, Mayor Pete Buttigieg and former Texas Rep. Beto O’Rourke — often seemed left out of the central clash, especially because they largely eschewed attacks on other candidates. Author Marianne Williamson received solid applause for answers on environmental racism and the water crisis in nearby Flint, Michigan.

The debate lacked a clear stand-out moment, but perhaps the strongest one came during another clash between Warren and Delaney. The onetime Maryland congressman had just said Democrats needed to avoid “impossible promises” and “fairytale economics” and focus on areas where the private sector and government can work together.

“I don’t understand why anybody would go to the trouble of running for president of the United States just to talk about what we really can’t do and shouldn’t fight for,” Warren replied.