As a U.S. senator, Jeff Merkley, D-Ore., makes $174,000 a year. So imagine his surprise a few months ago, when he learned the Cover Oregon health insurance exchange had enrolled him in the Oregon Health Plan, which covers only the poorest of the poor. Chalk up another embarrassing glitch for Cover Oregon, which remains a troubled work-in-progress after months of triage and more than $300 million in taxpayer money. A few months ago, Merkley opened the mail at his east Portland home to find he’d been enrolled in the Medicaid-funded Oregon Health Plan. The Oregon Democrat already had signed up...