President Trump speaks about the U.S. role in the Paris climate accord in the White House Rose Garden on Thursday. (Jabin Botsford/The Washington Post)

President Trump’s triumphant Rose Garden ceremony announcing his withdrawal from the Paris climate agreement sent a message loud and clear to his supporters: Promise kept.

But the move also served as a clarion call to angry Democrats, potentially complicating the political path for Republicans facing tough midterm challenges and, ultimately, Trump’s own reelection bid.

Trump, whose approval rating has hovered around 40 percent for most of his presidency, probably did not gain new converts with his decision, and Democrats now see an opportunity to further intensify the focus of their base in the 2018 midterm elections. They also foresee the climate-change decision as a key part of their broader argument to college-educated swing voters who have been among Trump’s weakest supporters.

“He’s unleashed a number of forces that I don’t think he understands that ultimately are going to work against him,” said Tad Devine, a longtime political strategist and former adviser to the presidential run of Sen. Bernie Sanders of Vermont. “People are interpreting this not as my house is going to be flooded tomorrow, but our federal government is being run by people who don’t care about science.”

Trump’s gamble could pay off. If the pace of economic growth quickens and jobs return for his core supporters, he could point to the decision to exit the accord as proof of his leadership, his backers say.

(Bastien Inzaurralde/The Washington Post)

“If the economy grows at a 3 percent clip, if in fact labor participation goes up, unemployment continues to drop from 4 to 3 percent, this in retrospect will look like a genius move,” said Ken Blackwell, who is the former mayor of Cincinnati and a Trump presidential transition official. “If we tailspin and go in the other direction, it will mean that our assumptions were wrong.”

Trump’s decision, which came despite the opposition of some in his administration including his daughter Ivanka, reflects the White House’s singular focus on holding on to his small but sturdy base of supporters — especially in the industrial Midwest — who helped him win the presidency.

“He’s going to be able to credibly say in the midterms that he pulled out of it and kept his promise,” said Republican political strategist Matt Mackowiak. “The question is if there’s a real-world benefit economically that his voters actually feel.”

The Democratic base, already strongly against Trump, needs little incentive to oppose him. But Democrats expect that Trump’s decision to leave the climate deal will serve more as a recruiting tool for their candidates in the midterms and in the presidential cycle.

Already mayors and governors, Democratic and Republican, have lined up to declare that they will pursue the United States’ climate goals with or without the federal government. And according to Gene Karpinski, president of the League of Conservation Voters, Trump has already been a force pushing Democratic candidates further to the left on the environment in gubernatorial races this year in New Jersey and Virginia, an effect that he expects will only intensify in 2018 and 2020.

“They know this is a critical issue for voters, and they’re competing to see how green they can be,” Karpinski said. “I think the decision underscores even more, when you look at the 2020 election, what’s truly at stake in terms of whether we’re going to be going forward or backward.”

(Daron Taylor/The Washington Post)

For college-educated moderates, including some Republicans, the issue could become emblematic of the Trump administration’s disdain for science and the long-lasting consequences of his leadership.

“It’ll affect Trump in that there are moderate Republicans who believe in science,” said Democratic pollster Anna Greenberg. “It has implications for the midterms if they’re not that excited about being involved in this mess.”

Climate change alone has never been much of a motivator for the electorate, although younger voters typically name it as one of their top issues in polling. A recent Pew Research Center poll found that 38 percent of Americans said it was a top priority, compared with 76 percent who name terrorism and 73 percent who said the same of the economy.

Yet climate change and the environment are issues that move political money in the Democratic world like little else. Major Democratic donors, such as financier and environmentalist Tom Steyer, who co-founded NextGen Climate, insist that Trump’s move is yet another provocation that will push younger people to become more engaged in politics.

“This is a very dramatic statement for that group of people about why you need to be involved politically,” Steyer said, including for those who have asked themselves in the past whether their vote matters. “This is a huge issue for them. They know that this will impact their lives dramatically.

“We will see if they turn out, but this is a shot across the bow,” Steyer said.

The challenge for Democrats remains in motivating voters to make climate change a ballot-box issue, which many in the party acknowledge is an uphill battle. Unlike health care, which virtually every person has a direct experience with, climate change seems far less urgent to many voters.

And Republicans have argued that the present-day economic needs of the country are more important than the less-certain possibility of harm to the planet in the future, an argument that Trump made in the Rose Garden on Thursday when he announced his withdrawal from the Paris accord.

“We will be environmentally friendly, but we’re not going to put our businesses out of work. We’re not going to lose our jobs,” Trump said. “I was elected to represent the citizens of Pittsburgh, not Paris.”

The risk for Republicans in the near term remains that even small shifts in enthusiasm could make the difference in competitive congressional races.

“All these things cumulatively spell real trouble for my party,” said Republican strategist John Weaver, who worked on Ohio Gov. John Kasich’s presidential bid. “It adds passion to the left, which brings us one step closer to Speaker [Nancy] Pelosi.”

Scott Clement contributed to this report.