A report issued by the nonpartisan Congressional Budget Office highlights faults with both sides of the argument to create a public health-insurance plan.

The CBO said only six million Americans would enroll in the public plan proposed in the 1,990-page health bill unveiled by House Democrats, according to findings issued late Thursday. That undercuts foes' claims that such a plan would lead to a government takeover of the health-care system.

One reason, according to CBO director Douglas Elmendorf's report: the public plan "would typically have premiums that are somewhat higher than the average premiums for the private plans" offered alongside it. That suggests the House bill could fall short of one of its major goals -- lowering insurance costs -- and presents those who...