NextGen Climate Action, the outside group run by billionaire environmentalist Tom Steyer, took a new tack in its attempts to bolster Democrats' chances in the Iowa Senate race this week. Its first ad, you migh recall, was a mini-play suggesting that Republican Joni Ernst had sold her soul to some shadowy cabal of dudes worried about tax breaks or something. The new ad is more to the point.

Iowans don't need clarification on the subtext. By cozying up to Big Oil, the ad suggests, Ernst displays disloyalty to ethanol — a biofuel that is usually made from corn and which the government has mandated be included in fuel mixes. That's in part out of the hope that the country could reduce the amount of carbon dioxide it emits. And the less carbon dioxide emitted, the slower the acceleration of climate change.

In Iowa, ethanol is generally popular. An industry survey conducted earlier this year put support for biofuel mandates at 65 percent nationally. Given that forty percent of the nation's corn crop went to ethanol production in 2012, according to experts writing for the Times, that's a lot of sales for Iowa corn farmers.

Tom Steyer (Jahi Chikwendiu/The Washington Post)

You know who doesn't particularly care for ethanol, though? Steyer, the man who is funding the ads. In an interview with Fortune in 2010, Steyer dismissed the use of ethanol in the national fuel mix.

"All the people who have met payrolls made investments, there’s a very sharp and ruthless measurement system for people like me," he said. "It’s just completely different. I saw in the paper the other day that Al Gore was saying that maybe he shouldn’t have been for ethanol. It’s kind of like, duh! Did you ever take out your calculator on that one?"

It's important to consider the first part of that quote alongside the second part. Steyer was echoing a broader transition by the environmental movement away from using biofuels to replace fossil fuels, but with an interesting rationale: It didn't pencil out. It wasn't the best means to the end. It wasn't practical.

There's been a debate in the environmental movement for some time about how best to address climate change. Should the movement oppose any non-doctrinaire measures on slowing global warming, hoping the fight reaches a tipping point? Or should it instead be pragmatic in an attempt to make slow — but achievable — change? This is a common struggle for change movements, of course, but for environmentalists, the looming threat of climate change has caused the debate to be energized by immediacy.

What Steyer and NextGen are doing in Iowa is being pragmatic. In 2006, leading environmental group Natural Resources Defense Council backed corn ethanol use, because plants consume carbon dioxide and biofuels burn more cleanly than oil. By 2011, its position had changed, in part because better biofuels exist. So why is NextGen blasting Ernst for turning her back on ethanol? Because it's pragmatic. If Iowans vote for Democrat Bruce Braley over Ernst because they want to sell more corn, good enough for NextGen. If Iowans vote for Braley over Ernst because they are worried about her selling her soul to a shadowy cabal, good enough for NextGen. If Braley wins over Ernst even though his opposition to the Keystone XL pipeline, a key priority for greens and Steyer, is soft? Good enough.

There's another technology that, like corn ethanol, has been considered a bridge between the old, high-pollution energy economy and the new, not-yet-existent clean one: Fracking. Hydraulic fracturing is a process that facilitates the extraction of oil and gas from shale deposits, and which created a massive boom in energy development in the upper Plains states. A huge influx of natural gas into the marketplace prompted some electricity providers to switch from coal to gas burning for generation — a big improvement in carbon dioxide emissions. At first, the Sierra Club backed natural gas as a way to lower carbon emissions. A few years ago, it changed its position, in part because of water pollution and on-site emissions concerns.

One group that didn't change its position on fracking was the Environmental Defense Fund. The group backs fracking, taking a high-profile grant from Michael Bloomberg to try and clean up the process and protect against the sorts of pollution that can result. That's a pragmatic, short-term goal — but one that frustrates other environmental groups that want to focus energy on more dramatic transitions away from carbon-intensive fuels.

The EDF's pragmatism is also on display in the 2014 election cycle. As the National Journal reported this week, EDF's political action committee is backing incumbent Rep. Chris Gibson (R-N.Y.) — despite his having a fairly poor environmental record by their standards. But he is a rarity within the Republican congressional caucus: He accepts the reality of climate change. Pragmatism.

In the case of both the EDF and NextGen, the goal is to slowly build a new Congress that is more receptive to arguments about the need for action on global warming. One Republican House member isn't going to ensure that the Congress passes climate-friendly policies, nor will a Braley win over Ernst ensure a climate-friendly Senate, even if Democrats hold the body. But, the argument clearly goes, you have to start somewhere, and purity can be the enemy of progress.

Meanwhile, activist environmental groups are gearing up for "a historic summit on climate change" scheduled to take place next month in New York City. It's a populist plan operating on a more immediate time frame. It may or may not be terribly pragmatic.

This post has been corrected to clarify between biofuels and biodiesel, which is not derived from corn.