WASHINGTON — In Michigan, an ad attacking Terri Lynn Land, the Republican candidate for the United States Senate, opens with a shot of rising brown floodwaters as a woman says: “We see it every day in Michigan. Climate change. So why is Terri Lynn Land ignoring the science?”
In Colorado, an ad for Cory Gardner, another Republican candidate for Senate, shows him in a checked shirt and hiking boots, standing in front of a field of wind turbines as he discusses his support for green energy.
And in Kentucky, a spot for the Republican incumbent Mitch McConnell, the Senate minority leader, depicts him flanked by coal miners as a woman intones, “The person fighting for our coal jobs is Mitch McConnell.”
Ads mentioning energy, climate change and the environment — over 125,000 spots and climbing on the Senate side — have surged to record levels during the 2014 midterm election cycle, reflecting the priorities of some of the nation’s wealthiest donors, with Democrats now pouring millions into campaigns to match Republicans, according to an analysis by Kantar Media/CMAG, which tracks political advertising.
In Senate races in the general election, the analysis found, energy and the environment are the third-most mentioned issue in political advertisements, behind health care and jobs.
The explosion of energy and environmental ads also suggests the prominent role that the issues could play in the 2016 presidential race, especially as megadonors — such as Thomas F. Steyer, a California billionaire and environmental activist on the left, and Charles G. and David H. Koch, billionaire brothers on the right — take sides. Leaders of major environmental groups like the Sierra Club and the League of Conservation Voters said they had collectively spent record amounts of money in this election cycle.
“Candidates are using energy and environment as a sledgehammer to win a race,” said Elizabeth Wilner, the senior vice president for politics at Kantar Media/CMAG.
Groups representing the energy industry and environmental advocacy have typically been the lead players in presenting policy positions in ads, but this year the candidates themselves and party political committees are also taking on that role.
In conservative states, Republicans are attacking Democrats for supporting President Obama’s environmental regulations. And in coal-mining states, each side is running ads showing its candidates embracing both the fuel and the workers.
In more liberal states, Democrats are attacking Republicans for denying the science of climate change and taking money from the Koch brothers.
“What’s important about what’s going on right now is the extent to which the Democrats feel confident playing offense on environmental and energy issues, and the extent to which polling shows that they are scoring when they do that,” said Geoff Garin, a Democratic pollster.
Mr. Obama’s new climate change policy prompted some of the ads. In June, Mr. Obama proposed an Environmental Protection Agency regulation that could shutter hundreds of coal-fired power plants — the nation’s chief source of planet-warming carbon pollution — and stand as the president’s climate legacy. That policy has galvanized Republicans against what they call a “war on coal.”
So far this year, nearly 47,000 spots have mentioned coal, while roughly 26,000 have mentioned the E.P.A. (The mentions have been almost entirely negative, except for spots in support of Senate Democrats, who have cited the agency in a positive manner more than 5,000 times.)
In the hotly contested Kentucky race between Mr. McConnell and Alison Lundergan Grimes, the Democratic challenger, both campaigns and outside donors have highlighted coal in ads.
“From a Kentucky standpoint, it made sense that this would be a bigger issue than Obamacare,” said Mike Duncan, a former chairman of the Republican National Committee who now heads the American Coalition for Clean Coal Electricity, a coal advocacy group.
In Colorado, Brad Todd, a Republican ad maker at OnMessage Inc. who is working on Mr. Gardner’s campaign, said the president’s policies have provided Republicans with material to attack Democrats. “President Obama has taken the Democrats too far left on energy,” he said, “and I think that’s really a metaphor for all the things they distrust about the president.”
In Republican-leaning states with economies that depend on fossil fuels, Democrats are promoting their support of those industries as a way to distance themselves from the president. Senator Mary L. Landrieu, Democrat of Louisiana, ran an ad trumpeting the ways in which her position as the chair of the Senate Energy Committee could help Louisiana oil companies.
In Democratic-leaning and swing states, the 2014 election cycle has seen a massive infusion of spending by liberal environmental groups that want to protect Mr. Obama’s legacy on climate change, while elevating the issue of climate change ahead of the 2016 campaign.
Chief among them is NextGen Climate, an advocacy group founded by Mr. Steyer, who has pledged that his group will spend a minimum of $100 million this year to elect candidates who back policies that would forestall climate change. The group has focused its spending on presidential battleground states like Colorado, Florida, Iowa, Michigan, New Hampshire and Pennsylvania.
“We picked states that will be relevant in 2016. These are all states that are key presidential swing states,” said Christopher Lehane, the group’s chief strategist.
The NextGen strategy is to spend heavily on advertising that attacks Republican candidates who question or deny the science of climate change.
Using polling and demographic data, the group has targeted a million of what it calls “climate voters” in Colorado, Florida, Iowa, Michigan and New Hampshire. The plan, said Mr. Lehane, will be to run even more ads aimed at those voters ahead of the 2016 elections.
Last week, the group released an ad depicting Republican candidates who dispute the science of climate change as cavemen. “The idea is that denying climate change is a path to political extinction,” Mr. Lehane said.
In Senate races in several key states, Democratic candidates, political committees and liberal advocacy groups also have run ads criticizing Republicans for their positions on climate change by tying them to other issues. In Colorado, the League of Conservation Voters ran an ad linking two key issues in the race — energy policy and women’s rights — and attacking Mr. Gardner, the Republican candidate, for opposing both environmental regulations and some forms of contraception.
“They’re making it part of the narrative that their opponents are outside the mainstream,” said Gene Karpinski, president of the League of Conservation Voters. “To the extent that it’s being used aggressively, that’s definitely new.”
During the 2012 presidential campaign, the issue of climate change did not come up once in the three debates between Mr. Obama and his Republican rival, Mitt Romney. This year, the Senate debates in Arkansas, Colorado, Iowa, Kentucky, Louisiana and West Virginia have all included robust exchanges on the candidates’ views on coal, climate change, energy and the E.P.A.
“I think the political intensity is only going to increase around this issue,” said Bill Ritter, the former Democratic governor of Colorado, who now runs an energy policy center at Colorado State University. “If you polled Republican governors around the country, you’d find that there’s an increasing number who are actually talking about it and trying to deal with it.”