The lead congressman investigating HealthCare.gov’s dismal performance during its first two months online ratcheted up the executive-congressional conflict on Wednesday, accusing Health and Human Services Secretary Kathleen Sebelius of criminal obstruction of his investigation. The dispute centers around a letter the Centers for Medicare and Medicaid Services sent to a contractor that worked on the online health insurance marketplace, directing it not to turn over correspondence and other documents to congressional investigators and stating CMS would manage any congressional inquiries. That letter amounted to “criminal obstruction” of a congressional investigation,” according to House Oversight and Government Reform Committee Chairman Darrell...