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It’s official: The 2020 Democratic presidential field is now awash with climate candidates.

Over the weekend, Gov. Jay Inslee of Washington announced that he would run, declaring himself the “only candidate who will make defeating climate change our nation’s No. 1 priority.”

In fact, every other Democratic presidential candidate has underlined his or her commitment to curbing planet-warming emissions — making the 2020 election much different from four years ago, when climate change was rarely mentioned.

“For far too long, climate change didn’t get nearly the attention that it deserved, either on the campaign trail or off, and that clearly has changed in a major way,” said Tiernan Sittenfeld, senior vice president for government affairs at the League of Conservation Voters.

In addition to Governor Inslee, Senators Cory Booker, Kirsten Gillibrand, Kamala Harris, Amy Klobuchar, Bernie Sanders and Elizabeth Warren have all identified climate change as a top campaign issue, as has John Hickenlooper, the former governor of Colorado. To varying degrees they have all also expressed support for the Green New Deal, a nonbinding congressional resolution that calls for a 10-year mobilization to dramatically reduce the burning of fossil fuels in the United States.

Some political scientists have suggested that extreme weather has made the issue of climate change more immediate for voters. Others say that President Trump’s denial of climate science has actually highlighted the problem. And the Green New Deal and one of its main sponsors, Representative Alexandria Ocasio-Cortez of New York, have sparked new enthusiasm among Democratic voters.

Thomas J. Pyle, the president of the Institute for Energy Research, a think tank that supports fossil fuels, said that, with so many Democratic candidates talking about climate, it would be harder for a candidate like Governor Inslee to stand out.

“If he ran in the last go-round he could probably distinguish himself as Mr. Green Jeans, but he’s just going to be one more voice in the choir promoting these extreme ideas,” Mr. Pyle said.