Health-care experts call it D.C. insiderism at its worst. The rumors began trickling in about a week before the scheduled vote on April 23: Republican leadership was quietly pushing senators to pull support for subpoenaing Congress’s fraudulent application to the District of Columbia’s health exchange — the document that facilitated Congress’s “exemption” from Obamacare by allowing lawmakers and staffers to keep their employer subsidies. The application said Congress employed just 45 people. Names were faked; one employee was listed as “First Last,” another simply as “Congress.” To Small Business Committee chairman David Vitter, who has fought for years against the...