Steyer, an environmentalist who is one of the party’s major financiers and who already hosted a fundraiser for Hillary Clinton, said he wants the debate to occur before the Iowa caucuses in February.

“Since the candidates — and the Democratic Party — understand that climate change is our greatest threat, they must allow voters the opportunity to hear a thoughtful and robust discussion — not just a single question — about their plans to solve this issue,” reads the release put out by Steyer’s group, NextGen Climate.

By wading into the conversation, Steyer could be putting real pressure on the Democratic National Committee, whose chairwoman Debbie Wasserman Schultz has maintained that the party would stick with its plan to hold six debates — four before Iowa — despite increasing pressure for more.

But the DNC showed no willingness to budge on Friday, instead suggesting that Steyer could host a candidate forum, not a debate.

"Given his commitment to progressive values, we believe that Mr. Steyer would be an ideal host of a presidential candidate forum — where all of the Democratic candidates can showcase their ideas and policy positions on this urgent issue," said spokeswoman Holly Shulman in a statement to POLITICO.

Wasserman Schultz has come under fire from two of the vice chairs in her own DNC, as well as presidential candidate Martin O’Malley, about the debate plan. Bernie Sanders has also urged the DNC to add more debates, while Clinton — who Steyer has not formally endorsed — has simply said she is open to participating in more.

But since O’Malley railed against the DNC leadership over its debate plan at the committee’s summer meeting in Minneapolis last month, new voices have popped up on both sides of the discussion. While House Minority Leader Nancy Pelosi joined O’Malley, DNC Vice Chair Hawaii Rep. Tulsi Gabbard, and DNC Vice Chair R.T. Rybak in urging the addition of more, a pair of close Clinton allies — Virginia Gov. Terry McAuliffe and Philadelphia Mayor Michael Nutter — said that would be overkill.

“Climate change is an urgent threat to our economy, health, and national security, and requires immediate and bold action from our next president,” explained Steyer. “The Democratic presidential candidates understand this and have acknowledged the urgency of the climate crisis. Now it’s time for them to tell us exactly what they’d do about it."

Steyer, whose wallet would be significant to any presidential candidate, recently praised Clinton over her opposition of the Keystone XL pipeline. But without formally throwing her his support, he has maintained political leverage over the party’s field.

The first Democratic debate is currently set for October 13 in Las Vegas.