While one of the AFL-CIO’s key health care reform principles—a public health insurance option—has been vigorously attacked by the private insurance industry, it received important backing last week from the Congressional Progressive Caucus (CPC).

The CPC long has backed a single-payer approach for health care reform. But last week, the group said that is not a line in the sand that could not be crossed to win its backing of health care reform legislation.

In a letter to congressional leaders, the CPC said its 77 members could support a public insurance plan option within a reformed health care system that maintained private insurance. But, the group also stressed that it’s the “minimum” needed to win their support for reform legislation.

The private for-profit insurance industry and most congressional Republicans long have opposed a public insurance option. After all, their soaring profits and bonuses are at stake. A public plan also is a central element of President Obama’s reform blueprint.

In a letter to House Speaker Nancy Pelosi (D-Calif.) and Senate Majority Leader Harry Reid (D-Nev.), the CPC wrote that caucus members want all Americans to have a choice of securing health insurance coverage under a public plan or through private insurance as part of any comprehensive health care reform legislation.

The diverse CPC is made up of House Democrats with progressive views on health care, the economy, global policy, the environment and other vital working family issues.

The Progressive Caucus co-chairs, Reps. Lynn Woolsey (D-Calif.) and Raul Grijalva (D-Ariz.), also wrote that while most CPC members prefer a single-payer plan as the best option. According to the letter, a public plan is a “minimum” and the “strong majority” of the 77-member group:

will not support legislation that does not include a public plan option that is supported on a level playing field with private health insurance plans.

House Majority Leader Steny Hoyer (D-Md.) said House Democrats are committed to including a public plan option in health reform legislation. But he told The Hill newspaper that although Senate Finance Committee Chairman Max Baucus (D-Mont.) has expressed support for a public plan, Baucus is working on developing bipartisan legislation with committee ranking minority member Chuck Grassley (R-Iowa), who opposes such an option.