Both Bloomberg and Steyer have unveiled a series of climate-related proposals after entering the race later than some of the current front-runners. Steyer, a former hedge fund executive, has called the matter his “number one priority.”

The two billionaires have a history of funding green initiatives. The former New York City mayor and owner of the Bloomberg financial empire has donated millions of dollars to The Sierra Club’s Beyond Coal campaign, which has worked to shutter numerous coal plants, and he has pledged to donate $500 million to close the country's remaining coal plants by 2030

Meanwhile, Steyer founded the organization NextGen America, which aims to support candidates who advocate for climate action.

“This is at the top of voters’ minds in 2020. We know that people are crying out to see action,” said Democratic strategist Jon Reinish. “I think it’s going to be a rewarding issue for both of them.”

Both have highlighted their commitment to the issue on the campaign trail.

Steyer has said that he would declare climate change a national emergency on his first day in office and Bloomberg has also said that fighting climate change would be a focus for him.

The push on climate change has come amid renewed attention to the issue in recent months following flooding in the Midwest, wildfires in Australia and other environmental disasters.

Although climate change is often identified by Democratic primary voters as a key concern, it hasn't always dominated the race. The Democratic National Committee, for example, did not heed calls by environmentalist groups for a debate solely debated to climate change.

Steyer and Bloomberg are now seeking to bring new attention to the issue.

“They have been super active and insistent at not only raising the profile of the issue in front of voters, making it a litmus test with elected officials, but also, especially if you look at Mike Bloomberg, using his resources ... to give big cities and major carbon users real incentives to plan for the future and a lower-carbon or carbon free future,” Reinish added.

Steyer’s camp said that his focus on climate will help promote the subject because of his ability to put it in an economic context.

“His message has expanded to put climate also in the context of our economic development and our need to have significant democratic reforms and really take back politics from corporations ... and give it back to the people,” said policy adviser Frances Sawyer.

Meanwhile, Bloomberg’s team stressed that their candidate provides a unique approach to the issue because he himself has “meaningfully reduced emissions."

“He has firsthand experience cutting emissions and cleaning up the air while at the same time growing the population of New York City, growing the economy,” said Antha Williams, Bloomberg’s senior adviser on climate, energy and the environment.

Bloomberg this past week put out a plan calling for greener buildings and homes through "aggressive clean building codes" and incentivizing pollution-free and electric options for people looking to replace appliances or equipment. He also this week said he would aim for all new cars to be electric by 2035 and said he would implement mileage and pollution standards.

However, both candidates have faced a certain degree of skepticism on climate issues and they also have to contend with candidates who are polling higher than they are and who have also put heavy emphasis on climate policy.

Environmental group Greenpeace has questioned whether Bloomberg has provided enough details on his climate change plans.

“We expect that Mayor Bloomberg will come out with some more detailed plans given his record, but at this point, we just haven’t seen those yet,” said Jack Shapiro, Greenpeace’s climate leadership project lead, before the release of Bloomberg’s housing and transportation plans this week.