A third federal judge upheld the constitutionality of the Obama health care law on Tuesday, reinforcing the divide in the lower courts as the case moves toward its first hearings on the appellate level.

Judge Gladys Kessler of Federal District Court for the District of Columbia became the third appointee of President Bill Clinton, a Democrat, to reject a constitutional challenge to the Affordable Care Act. Two other federal district judges, both appointed by Republican presidents, have struck down the law’s keystone provision, which requires most Americans to obtain health insurance starting in 2014.

One of those judges, in a case filed in Florida, ruled that the rest of the law could not be severed from that provision, and suggested that the entire act was therefore invalid. The Justice Department, which represents the Obama administration in the cases, has asked the judge for clarification of his ruling, which left states confused about whether to continue carrying out the law.

Although the issue will almost certainly be determined by the Supreme Court, each lower court ruling contributes to the balance of legal opinion that the justices will consider. More than 20 challenges to some aspect of the sprawling act have been filed around the country. Oral arguments in the first appellate reviews are scheduled for May and June.