Progressive candidates Bernie Sanders and Elizabeth Warren bore the brunt of attacks from more moderate rivals in the second round of U.S. Democratic debates on Tuesday, spotlighting the ideological divide among the party’s crowded presidential field.

The Democrats on stage were united in stressing the urgency of defeating Republican President Donald Trump in the November 2020 election, but delivered bruising critiques of their party rivals’ positions on issues like healthcare and immigration.

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Democrats battle for breakout moments

Trump has been eager to paint the entire Democratic field as socialists, seeking to make any eventual nominee untenable to voters by arguing Democrats want to raise taxes, open the U.S. borders and take away private healthcare.

The dispute between the moderate and liberal wings of the Democratic Party highlighted central question of the nominating contest: Which candidate in field of more than two dozen would be best positioned to beat Trump next year?

Progressives argued their policies would excite voters and allow them to draw a distinct contrast to Trump.

Taking a jab at former U.S. Representative John Delaney, who often played the role of liberal foil during the debate, Warren said: “I don’t understand why anybody goes to all the trouble of running for president of the United States to talk about what we really can’t do and shouldn’t fight for.”

As the front-runners in the polls among the candidates debating on Tuesday, Sanders and Warren, both U.S. senators, often found themselves defending the policy positions they share.

"I get a little bit tired of Democrats afraid of big ideas. Republicans are not afraid of big ideas,” Sanders said.

Lower-tier candidates were aiming to produce the kind of post-debate surge that U.S. Senator Kamala Harris enjoyed after a strong performance in the first debate after confronting front-runner Joe Biden on the issue of race.

The two nights in Detroit could be the last chance for many contenders to debate on the national stage, as the Democratic National Committee will double its fundraising and polling requirements to qualify for participation in the next debates in September and October.

Ten more candidates will face off on Wednesday night, including Biden and Harris.