Together, those developments are resounding successes for the climate activists. But based on his performance Wednesday night, Joe Biden probably wishes no one had listened to them. The former vice president repeatedly rambled and stumbled through his answers, at one point cutting himself off with “Anyway, I’m taking too long. Sorry.” He criticized the Green New Deal because it “doesn’t have a lot of specifics” just days after he said “details are irrelevant in terms of decision-making.” And he tried to brag about his climate plan receiving a “B-plus or beyond” from climate groups, leaving out that those groups gave higher ratings to plans from other candidates including Sen. Bernie Sanders (I-Vt.).

But his worst moment came when a student asked him about a fundraiser Biden is scheduled to attend Thursday, one that is co-hosted by Andrew Goldman, a co-founder of natural gas company Western LNG. Wasn’t this a violation of Biden’s promise not to take money from the fossil fuel industry? “Well, I didn’t realize he does that,” replied Biden — hardly an acceptable standard. Biden’s team would later double-down by arguing that Goldman is no longer involved in the company’s day-to-day operations, a denial that’s hard to take seriously when Goldman is still listed second on Western LNG’s leadership page, ahead of two senior vice presidents.

All in all, it was another tough night for Biden. By contrast, the two most progressive candidates in the race, Sanders and fellow Sen. Elizabeth Warren (D-Mass.), have to be pleased with Wednesday evening. For Sanders, the town hall was a vindication that his $16 trillion climate plan is the benchmark for ambitious responses to climate change: Several other candidates, including Warren, were asked to compare their plan to his. Perhaps his best moment came when he was asked what would happen to Americans employed in the fossil fuel industry:

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The coal miners in this country, the men and women who work on the oil rigs, they are not my enemy. What is my enemy is climate change. And what we have done is build into our plan, our $16 trillion plan, tens and tens of billion of dollars for what we call a just transition. And that says that if some worker through no fault of his own or her own loses their job because we’re moving away from fossil fuel, we’re going to guarantee them an income for five years, we’re going to guarantee them the education that they need, because those workers are not our enemies. They should not be punished because we’re trying to save the planet.

Like Sanders, Warren was crisp, clear and, unsurprisingly, full of detail. She had the best response of any candidate to the CNN hosts’ consistent questions about regulations on plastic straws, eating meat and, in Warren’s case, lightbulbs: “Oh, come on, give me a break. … This is exactly what the fossil fuel industry hopes we’re all talking about. … They want to be able to stir up a lot of controversy around your lightbulbs, around your straws and around your cheeseburgers, when 70 percent of the pollution, of the carbon that we’re throwing into the air, comes from three industries” — referring to oil, building and electric power, according to the New York Times.

If anything, Warren’s biggest problem was how similar she was to Sanders. Again and again she echoed his views on taking on corporations and the urgency of fighting climate change. On nuclear power, for example, where she could have drawn a contrast with Sanders, Warren agreed with him. All of this led to an awkward final question where she couldn’t really explain why her climate plan isn’t as large as Sanders’s.

Of course, a few town halls, even if they surpass all ratings expectations, won’t change the course of the Democratic primary. But in giving this time over to this critical issue, CNN did the public a service — not just by giving climate change the airing it deserves but also helping voters really sort through Democrats’ differences. For Biden, that contrast was hardly a welcome one.