The Seattle Times editorial board supports the lawsuit of state attorneys general, joined by Washington Attorney General Rob McKenna, that challenges the constitutionality of the new federal health-insurance law.

THE politically orchestrated hiss at Rob McKenna has not been convincing. Washington’s attorney general has the clear authority to argue that the new health-insurance law violates the Constitution, and to sign on to a lawsuit to that effect.

Opponents ask, “Who is McKenna’s client?” It is the people who elected him. Note that a Survey USA poll suggested that more Washington voters agree with him (44 percent) than do not (40 percent).

Opponents ask how much the lawsuit by 13 state attorneys general costs the people of Washington. It doesn’t cost them any extra money. The state of Florida is paying for it.

Opponents imply there is something outrageous in challenging a new law. It is not outrageous. It is part of the American system. Think of the Tim Eyman tax initiatives. Almost all the ones that passed have been challenged.

The main challenge here is on one point — whether the federal government can require people to buy a private product: health insurance.

The argument centers on the U.S. Constitution’s commerce clause, which gives Congress the power “to regulate Commerce … among the several States … ” The lawsuit argues that requiring a citizen to buy insurance goes beyond regulating commerce. It is, says McKenna, “forcing people into the stream of commerce.”

The law calls its mandate a tax. But if you comply, your money goes to the insurance company. You pay the government only if you don’t comply — which means, McKenna says, “It’s not a tax. It’s a fine.”

We think McKenna has a good case, and one the progressives who condemn him ought to appreciate. These critics are so often right about the dangers of corporate power, and particularly the rapacity of insurance companies.

But if it’s federal power, and it’s for a social purpose, and Barack Obama is presiding over it, they set their judgment aside. They accept a 2,000-page bill on its label only. They accept its promise, almost surely vacant, of cost savings. They overlook the deals cut with the insurance and pharmaceutical interests. They shrug off the “cornhusker kickback.” And to those who invoke the Constitution, they become shrill.

This page supported Obama, and we still like him. But we also support checks and balances on federal power, and review of this law by the Supreme Court.