NEWARK — On climate change, capital punishment and drug addiction, three Democratic candidates running for Delaware’s lone seat in the U.S. House of Representatives were in agreement Tuesday.

Newark Sen. Bryan Townsend, 2014 state treasurer nominee Sean Barney and former candidate Mike Miller laid out their cases in a debate at the University of Delaware, touting their liberal credentials before an audience of students, lawmakers and rank and file Democrats.

Organized by the university’s College Democrats, the event featured the congressional hopefuls answering questions from a student moderator.

Though the three men took similar stances on most issues, the debate did provide an opportunity for them to try and highlight their differences and backgrounds.

Mr. Barney repeatedly pointed to his time as a U.S. Marine and working for Sen. Tom Carper, D-Del., and Gov. Jack Markell, while Sen. Townsend cited bills he supported in the General Assembly.

The three candidates all spoke in favor of criminal justice reform and more governmental oversight in many areas. With few exceptions, they avoided confrontations with one another, opting not to issue criticisms but to detail their views and ideas.

Mr. Miller did challenge Sen. Townsend on his plan to change the tax code, but his questioning was shot down by the moderator for lack of time.

Sen. Townsend, who received the loudest applause when the candidates were introduced, played to the audience, several times urging students to help with a grassroots push.

Questions concerned foreign policy, free trade and the environment, with the speakers taking similar positions.

One question concerned DuPont, the chemical giant that announced a merger with Dow Chemical in December and later, after lobbying from Delaware officials, revealed plans to keep two of the subsequent spinoff companies in the state.

Citing the jobs and revenue that would be lost if the company moved, both Mr. Miller and Mr. Barney agreed the tax incentives were needed. Sen. Townsend was more hesitant and said changes to the tax structure were important to prevent DuPont leaving, but he also called for considerations of how money is spent to aid corporations.

“We need to insist on good outcomes, we need to insist on measurables, we need to insist on doing right by the taxpayer and many people who depend very understandably on important government services,” Sen. Townsend said.

Although they professed views that are broadly very similar, the candidates did differ on free community college, a proposal backed by President Obama.

Sen. Townsend and Mr. Barney stressed the importance of education, particularly affordable higher education, while Mr. Miller called the idea a “noble thought” but said “the bottom line is someone has to pay for it.”

All three proclaimed support for criminal justice reform, elimination of the death penalty and expanded substance-abuse treatment.

“People talk about being soft on crime if you try to make sure that opportunities await someone coming out of prison. But it’s not soft, it’s smart policy,” Sen. Townsend said.

Mr. Miller detailed a proposal that would have the state spend $20,000 more per prisoner to provide rehabilitation services, such as transitional housing and job training, designed to reduce recidivism.

Mr. Barney affirmed his support for abolishing the death penalty, claiming black men are executed at a disproportionate rate.

“If we are honest with ourselves, it is clear historically and today the death penalty in practice is not providing equal justice in the law,” he insisted.

All three agreed on reducing carbon emissions and fighting climate change. Sen. Townsend accused Republicans of rejecting “basic science” and Mr. Barney called a recent Supreme Court ruling halting a clean-power plan “a new low” from the court.

Mr. Miller said the tax code needs to be simplified and pointed to his work as an accountant as evidence of what makes him qualified for the House.

“I understand the tax code. I understand what goes off it,” he said. “I’ve been doing it for 23 years.”

Former state Labor Secretary Lisa Blunt Rochester was scheduled to attend but dropped out of the debate several days ago.

“Unfortunately, Lisa had another commitment that prevented her from attending tonight’s debate,” her campaign manager, Max Glass, said.