When Democratic strategist Bill Burton went looking for a partner to help his super PAC launch a $1 million ad campaign announced last week, he had more than one reason to knock on the door of the League of Conservation Voters.

The 43-year-old environmental group has ramped up both its political spending and its lobbying activity this year. And Democrats, tired of playing defense in a recent series of debates on climate and energy policies, are trying to turn environmental issues to their advantage.

“One of the lessons learned from the failure to pass a comprehensive clean energy bill back in 2010 is that we need to be smarter and sharper and more focused in our legislative accountability work,” LCV President Gene Karpinski said.

As GOP-friendly super PACs and nonprofits dramatically outraise their progressive counterparts, the LCV has responded aggressively. It was among the first Democratic-friendly groups to set up a super PAC of its own in 2010, spending $5.5 million in that cycle.

In this election, the group has already spent more than $4 million, about half of which went toward attacking Sen. Scott Brown (R-Mass.) for voting to protect tax breaks for oil companies. Brown publicly denounced the ads and went on to sign a pact with his Democratic opponent, Elizabeth Warren, aimed at keeping outside groups from spending money in the race.

The LCV’s $1 million ad campaign with Burton’s Priorities USA Action, which backs President Barack Obama, takes a similar tack, assailing presumptive Republican presidential nominee Mitt Romney for protecting the oil industry’s “profits and billions in special tax breaks.”

“Voters are particularly concerned about the fact that huge oil companies so badly want Mitt Romney to win this election,” said Burton, a former Obama White House aide who is a senior strategist for Priorities USA Action. He said Romney’s candidacy “has been tremendously motivating for voters who are animated by concerns about clean air and clean water.”

Democrats are hoping their green base will mobilize, pointing to news reports that petroleum and chemical industry billionaires David and Charles Koch will steer $200 million to politically active conservative groups before the election.

Obama himself suggested in a recent interview with Rolling Stone magazine that the issue of climate change could resonate with voters this year, prompting a Washington Post editorial urging Obama to take action on that front.

But the ongoing recession has pushed environmental concerns to the back burner, political experts say. Democrats have taken a beating over rising gas prices and the construction of the Keystone XL pipeline, which some labor unions support.

“It’s going to be really hard for the Democrats to mount an effective pro-environment stance when it’s very easy to make the case that environmental regulations damage the economy,” said Michelle Pautz, an assistant professor of political science at the University of Dayton.

A recent Gallup poll found that voters favor economic growth over protecting the environment, 49 percent to 41 percent. That’s a smaller margin than last year, according to Gallup, when the economy trumped environmental protection by 18 points. But it’s a reversal from polls before the economic downturn: One 2007 survey found that voters prioritized the environment over the economy 55 percent to 37 percent.

Still, the LCV’s bid to raise its profile has caught the attention of Democratic leaders. The group spent upward of $300,000 on ads favorable to Sen. Sherrod Brown (D-Ohio), who has faced a barrage of broadcast attacks by GOP-friendly groups. The LCV is focusing principally on Senate races in Montana, New Mexico and Virginia and has bundled more than $400,000 for candidates in this cycle, another record.

The activity includes promoting issues and policies in the hope of growing the group’s grass-roots membership, which recently topped 500,000. The LCV also leverages its environmental scorecard and its affiliation with almost three dozen state leagues.

Not all Democrats are cheering, though. Last week the LCV trumpeted its role in helping oust incumbent Blue Dog Democrat Tim Holden (Pa.), who lost his primary to lawyer Matt Cartwright. The LCV wasn’t the only outside group active in the race, but its $230,000 ad campaign aimed at Holden was the biggest of any other outside player.

The LCV’s role toppling Holden ruffled some feathers among Democratic leaders. However, Karpinski noted it was not the first time his group intervened to help an upstart candidate.

In 2004, the LCV spent $400,000 to help a little-known Democrat win a Senate primary in Illinois — a candidate who now happens to occupy the White House. Said Karpinski with some satisfaction: “He remembers to this day.”

Correction: May 1

An earlier version of this article gave an incorrect time frame during which the League of Conservation Voters spent $4 million. The LCV spent that amount so far in this election cycle.