The League of Conservation Voters has thrown down the gauntlet in its campaign to win support for the American Clean Energy and Security Act (ACES) when it could see a U.S. House vote as soon as Friday.

The politically-potent organization, that has made its endorsement something akin to the Good Housekeeping seal of approval for candidates seeking to position themselves as environmentally sensitive, announced Tuesday that it would not support the reelection of any House member who opposes the measure that it says "has the potential to transform America by creating clean energy jobs, improving our national security, and protecting our planet from global warming pollution."

In a letter to House members, LCV President Gene Karpinski wrote, "The stakes could not be higher; a safer, healthier planet and a new energy economy hang in the balance, and it's imperative that members of Congress be on the right side of history."

That makes it sound as if, for environmentalists, the choice to back this bill is a no-brainer.

It's not.

There is a significant divide within the environmental community over the measure that is being backed by the Obama administration and House Democratic leaders.

As the LCV was threatening to pull its endorsement from dissenting members, Friends of the Earth launched a campaign to block the bill. "Corporate polluters including Shell and Duke Energy helped write this bill, and the result is that we're left with legislation that fails to come anywhere close to solving the climate crisis. Worse, the bill eliminates preexisting EPA authority to address global warming--that means it's actually a step backward," says FOE president Brent Blackwelder, a veteran campaigner –- who has often been ahead of the curve when issues of economics and the environment are in play.

Blackwelder argues that, "Last November, the American people voted for change. Unfortunately, while the party in power may have changed, the process through which this bill was negotiated makes it clear that the overwhelming influence of corporate special interests has not. This exercise in politics as usual is a wholly unacceptable response to one of the greatest challenges of our time, and it endangers the welfare of current and future generations. Speaker Pelosi and congressional Democrats simply must do better. We are calling on them to vote against this bill unless it is substantially strengthened. If the ‘political reality' at present cannot accommodate stronger legislation, their first task must be to expand what is politically possible --- not to pass a counterproductive bill."

Does Blackwelder stand alone?

Not hardly. Even groups that back the bill, such as the Sierra Club, admit it has serious weaknesses.

And a number of top environmental groups have been bluntly critical of ACES.

After the House Energy and Commerce Committee completed work on the measure, Greenpeace USA Executive Director Phil Radford said, "Despite the best efforts of (Energy and Commerce Committee Chair Henry) Waxman, this bill has been seriously undermined by the lobbying of industries more concerned with profits than the plight of our planet. While science clearly tells us that only dramatic action can prevent global warming and its catastrophic impacts, this bill has fallen prey to political infighting and industry pressure. We cannot support this bill in its current state."

Around the same time, a coalition of more than a dozen national, regional and state environmental groups – including FOE and Greenpeace USA -- announced that:

Regrettably, we cannot support this legislation unless and until it is substantially strengthened. The lives and livelihoods of 7 billion people worldwide will be affected by America's response to the climate crisis. The response embodied in today's bill is not only inadequate it is counterproductive.

As passed through the Energy & Commerce Committee, the American Clean Energy and Security Act sets targets for reducing pollution that are far weaker than science says is necessary to avoid catastrophic climate change. The targets are far less ambitious than what is achievable with already existing technology. They are further undermined by massive loopholes that could allow the most polluting industries to avoid real emission reductions until 2027. Rather than provide relief and support to consumers, the bill showers polluting industries with hundreds of billions of dollars in free allowances and direct subsidies that will slow renewable energy development and lock in a new generation of dirty coal-fired power plants. At the same time, the bill would remove the President's authority to address global warming pollution using laws already on the books.

The Center for Biological Diversity is especially dubious.

The conservation group has been alerting members to flaws in the bill:

This Friday, June 26, Congress is expected to vote on a global warming control bill called the American Clean Energy and Security Act. If implemented, the bill would give all of us less than a 50/50 chance of avoiding catastrophic runaway global warming. And it repeals the power of other laws to act as a global warming backstop, effectively putting all our eggs in one precarious basket.

Leading scientists warn that the amount of carbon dioxide in our atmosphere must be reduced to no more than 350 parts per million to combat the climate crisis. But the American Clean Energy and Security Act sets a goal of allowing atmospheric carbon to increase to more than 450 parts per million. At that level, scientists say global warming could cause catastrophic impacts to humans and other species.

The bill also cripples the Clean Air Act, one of our nation's best tools for curbing air pollution. Under the American Clean Energy and Security Act, the Clean Air Act's ability to regulate critical polluters would be repealed, and numerous coal-fired power plants could be built without any additional emissions-reduction requirements for more than a decade into the future.

The American Clean Energy and Security Act is currently not strong enough to fight the climate crisis.

The debate about this legislation is playing out on several levels. Of course, there are many dead-ender Republicans, who are opposing this ACES legislation because their campaign-contribution paymasters in the corporate sector are against it. Some rural Democrats have been critical of the measure because they think its approach will hit farms and rural communities too hard.

But there are also progressives who say that this bill is an insufficient response to an epic challenge -– and that in some areas it could do more harm than good.

The LCV's our-way-or-the-highway approach fails to take into account the sincere opposition to the America Clean Energy and Security Act. That is a mistake, as the criticisms advanced by the Friends of the Earth and other groups are legitimate expressions of concern about a measure that Progressive Democrats of America in a letter to key House members on Wednesday described as "seriously flawed" and "a step backward, offering inadequate responses to our urgent needs."

"We urge the Congressional [Progressive and Black] Caucus to mobilize to strengthen this bill so that it merits your support," read the letter. "Alternatively, if the bill cannot be substantially improved, we urge you vote "no" on the floor."