Tensions are rising ahead of a July 9 court argument in the legal fight to save or kill Obamacare.

Democrats are pushing Trump administration officials to explain why it is now advocating for the entire health-care law to be struck down. The Justice Department typically argues to uphold U.S. law.

At the same time, a federal appeals court wants Democrats to explain before the July 9 appeal arguments why they should even be allowed to defend the law.

House Oversight Committee Chairman Elijah Cummings (D-Md.) sent a letter to Acting Office of Management and Budget Director Russell Vought June 26...