When Sens. John Kerry (D-Mass.) and Joe Lieberman (I-Conn.) unveiled their long-awaited American Power Act last week, it drew two sharply different responses from two collections of activist groups.

Two hundred groups that might be called “little green” immediately condemned the climate and energy bill in a joint letter, calling it “greenwashing in the extreme.” The coalition consists of regional environmental, peace, and religious groups — such as Don’t Waste Arizona, the Snake River Alliance, and the Turtle Island Restoration Network.

“This bill is just business-as-usual: taxpayer giveaways to giant nuclear and other energy corporations wrapped in the guise of doing something about our climate crisis,” they wrote.

Big Green issued its own statement the same morning. It was neither an endorsement nor an attack on the bill. It was thoroughly — impressively — devoid of any clear opinion of the bill.

“It is time for America’s leaders to get serious … the Gulf Coast oil catastrophe is yet another reminder … President Obama and leaders of both parties in Congress must provide the leadership necessary to develop a clean energy and climate solution,” said the joint letter from 23 larger and more D.C.-centric groups, including Environmental Defense Fund (EDF), the Sierra Club, Audubon, and the League of Conservation Voters.

The Kerry-Lieberman bill is undoubtedly flawed from an environmental perspective; in addition to giveaways for the nuclear, oil, and coal industries, there are the weak emission-reduction targets and the heavy reliance on carbon offsets. Every concession to polluter interests was added in hopes of luring enough fossil-fuel-beholden senators to reach the painfully difficult 60-vote threshold. That’s considered the only realistic way to pass a climate bill in 2010. Kerry, in a Grist post, implored greens not to slam the bill because it’s too weak, saying it’s better to get started with an imperfect bill.

This all puts green groups in the thorny position of having to either endorse flawed, compromise-laden legislation or oppose the closest thing to a decent climate bill we’re going to see this year, and perhaps for years to come. Many big green groups will probably end up supporting the bill, but don’t want to tip their hand while there’s still a chance to improve it. Hence the awkward non-comment last week. Many activist-oriented groups — including the 200 signees and notable big dogs Greenpeace and Friends of the Earth — have already made their opposition known.

Courtesy Climate SOSThis is far from the first inter-movement dispute among green groups. Last fall I reported on a “no compromise” faction of liberal groups that attacked Al Gore, the Waxman-Markey House bill, and carbon markets that allow polluters to buy and sell emissions credits. They argued that larger environmental groups had given away too much in collaborating with businesses and Democratic lawmakers. Reps from EDF, the Natural Resources Defense Council, and the Center for American Progress found this, shall we say, annoying.

Two kinds of hope

So which approach is, y’know, better for saving the earth?

It’s worth noting that all the groups involved have shown they understand the scientific urgency of an aggressive clean-energy plan. And they all want President Obama to use his bully pulpit to give the issue more attention. The disagreement is about political strategy.

At first blush, the left wing of the environmental movement seems to have the more optimistic approach, refusing to settle for a faulty bill and betting that it can create a groundswell of support for more hard-hitting climate legislation over the coming year or two — enough to force members of Congress to turn its way, or force out members of Congress who don’t.

The Big Green groups look to have the more pessimistic approach by supporting a crappy bill. They say they don’t see a path to a better one in the immediate future. Even getting the Kerry-Lieberman bill passed would be a huge uphill battle. And with Republicans poised to gain a number of seats in both the House and Senate in November’s midterm elections, the chances of passing any climate bill at all next year or the year after — let alone a better bill than Kerry-Lieberman — seem even more remote.

Here’s the counter-argument: Big Green is embracing a different kind of optimism. They are banking on the notion that building a clean-energy economy will be cheaper and easier than expected, and that once we get started, even with weak half-measures, success will follow upon success.

David Roberts explained this view last week: “Right now, policy is being made out of fear: fear by the private sector that decarbonization will be a crushing burden; fear by consumers that their energy prices will skyrocket; fear by politicians that the project will prove electorally unpopular.” But there are “huge opportunities for low-cost (or negative-cost) emission reductions just waiting to be exploited,” he argues. If a weak bill gets that process started, it can alleviate fears, begin moving the country in the direction of a clean-energy economy, and make it easier to pass stronger legislation down the line.

So either camp can claim to be more hopeful — one in the short term and one in the long term.

The problem is that by working against each other, they sap enthusiasm for building a popular movement for climate action. Lots of Americans would like to see the U.S. move toward a clean-energy economy and address the climate threat — 61 percent of respondents said so in a recent poll. But squabbles among environmentalists risk turning them off.

And building a diverse movement should be goal No. 1, according to author and 350.org organizer Bill McKibben. He argues that lawmakers don’t yet feel pressure from the public to take the climate threat seriously. “There are lots and lots and lots of groups lobbying Congress,” he told Grist in January. “But Congress members are good at telling whether there’s anything behind that lobbying or not. I think we have to figure out how to put some pressure behind that lobbying.” Until then, he argues, the focus on Congress is premature.

He may be right that movement-building — the focus of 350.org — is the long-term imperative. But there’s a bill in the Senate that demands a response right now.

So how should environmental organizations and concerned citizens respond to the bill? What’s the best way to built momentum toward a strong climate movement? And how do we get started with solutions as soon as possible?