http://www.nytimes.com/2011/04/12/us/politics/12missouri.html?_r=2&hpw

KANSAS CITY, Mo. — Missouri’s Democratic attorney general broke with his party on Monday and urged a federal judge to invalidate the central provision of the new health care law.

The filing of the brief by Attorney General Chris Koster, a onetime Republican state legislator who switched to the Democratic Party in 2007, underscores the act’s political tenuousness in a critical Midwestern swing state.

Mr. Koster’s action followed months of pressure from state Republicans that he join attorneys general from other states who are challenging the constitutionality of the law.

Rather than join the litigation, however, Mr. Koster chose to file a “friend of the court” brief in the United States Court of Appeals for the 11th Circuit, in Atlanta, which is reviewing one of five challenges to the act that have moved into the midlevel appellate courts.

Three lower court judges have upheld the law, while two have ruled that its central provision — the requirement that most Americans obtain health insurance — is unconstitutional.