As the United States gets closer to the presidential elections, climate change is gaining momentum among one of the top priority issues for most Democrat voters, showing a big gap with Republican voters.

While healthcare remains the main issue for Democrats, climate change ranks in a close second place, according to a new survey by Climate Nexus, a nonpartisan nonprofit group.

Nearly 2,000 registered voters showed global warming has become a key issue in American politics, alongside the economy, jobs, immigration, and social security. For democrats, this is now nationally the most important issue, the survey showed.

The poll was done online in 26 states, each of them set to hold a Democratic primary between now and the end of March. Climate Nexus partnered up with the Yale Program on Climate Change Communication and the George Mason University Center for Climate Change Communication.

“This is the first time in American political history where climate change is not just a top-tier issue—it is the top-tier issue,” Antony Leiserowitz, the director of the Yale Program on Climate Change Communication, told The Atlantic.

While Democrat voters seem to be more engaged with climate change, that’s not the case of Republicans, according to the poll. Democrats are by far more likely to consider the issue as one of the priorities than Republicans, showing a big divide among voters.

The Democratic primaries so far have reaffirmed the results of the survey. In Iowa, New Hampshire and South Carolina climate change were among the top three issues, according to the AP’s VoteCast exit polls.

Earlier this year, a survey by the Pew Research Center showed nearly two-thirds of Americans ranked protecting the environment as a leading policy priority, but with a big divide among Democrats and Republicans on climate change.

The Democratic Party has put a strong focus on climate change in this year’s presidential elections, with all presidential hopefuls claiming they would implement strong climate action plans to reduce greenhouse gas emissions.

Republicans also introduced a climate agenda, pushing an initiative to plant one trillion trees by 2050, likely addressed to younger Republican voters, who are more in line with climate action. Nevertheless, experts have said the effort is largely not sufficient to avoid global warming to continue.

There are still big misperceptions about climate change and the ecological crisis among United States citizens, a survey last year showed. The survey asked more than 1,000 people how many of the past 22 years have been among the hottest. Despite the correct answer being 20, the average answer was 14.