Joe Biden is facing questions about whether he violated a "No Fossil Fuel Money" pledge, after attending an Upper West Side fundraiser organized by the founder of a natural gas company.

The former vice president and current frontrunner for the Democratic nomination was in town this week for a forum on climate change hosted by CNN. On Thursday night, he slipped into Majestic for an event hosted by banker David Soloman and Andrew Goldman, co-founder of the liquified natural gas company Western LNG.

While Biden vigorously denied that the appearance was at odds with his own pledge to reject financial support from the fossil fuel industry, dozens of climate activists who'd gathered outside the Central Park West building held a different view.

"I think it violates the spirit of the pledge, if not the word," Matthew Miles Goodrich, an organizer with the grassroots group Sunrise Movement, told Gothamist on Friday. "Goldman is the founder of a natural gas company, and the reality is that natural gas does not have any role in this country under the Green New Deal, and certainly not in a livable future for our generation."

Biden's campaign team has countered that Goldman is no longer involved in day-to-day operations of the company. But the Times notes that he is still listed as LNG's co-founder, and a company press release from last year describes him as a “a long-term investor in the liquefied natural gas sector.”

(Solomon, for his part, is the scion of Hildred Capital Partners and former VP of Forest Laboratories, which previously coughed up $313 million to settle claims that it was illegally marketing antidepressants to children.)

According to a pool report, Biden addressed this tension with Berman during the fundraiser, though stopped short of explaining how exactly his appearance squared with his commitment. "I just want to be very clear to everyone here: I am committed to not raising money from fossil fuel executives and I am not doing that tonight,” he told attendees. "Climate change presents an existential threat, and it is real."

Biden is not alone in his questionable adherence to the fossil fuel pledge, which just about every Democratic candidate has signed onto in recent months. Atlas Energy, a holding company that invests heavily in oil, gas, and coal operations, donated over $5,000 to Pete Buttigieg's campaign in June, months after he signed the pledge. Buttigieg eventually returned that money, though only after the conflict was disclosed by the news outlet Sludge.

Environmentalists say they were surprised by Biden's decision to sign the pledge, and many had positive things to say about the candidate's climate plan released earlier this summer, which included a $1.7 trillion federal investment in clean energy. He'd previously faced harsh criticism from activists, after his campaign previewed a "middle ground" approach to the climate crisis.

But Thursday's fundraiser, advocates said, casts further doubt on the campaign's commitment to the sort of radical climate action that is broadly popular with the public.

"That he still has fossil fuel executives in his inner circle really puts into doubt his seriousness when it comes to climate change and winning the Green New Deal," said Goodrich.

A spokesperson for the Biden campaign did not respond to Gothamist's inquiries.