For U.S. Sen. David Vitter, R-La., the federal health care law is the gift that keeps on giving.

Not that he likes the Affordable Care Act, which is more popularly known as “Obamacare” and ranks as the signature legislative achievement of Democratic President Barack Obama. Like virtually all Republicans in Congress, he hates it, and he has filed a bill to repeal it in toto.

But there’s a particular aspect of the act that especially sticks in Vitter’s craw, and his engagement — some would say obsession — with it has provided him material for news releases and floor speeches and additional legislative proposals. The object of Vitter’s focus is the so-called “Obamacare” exemption for members of Congress and their staffs. The issue has its roots in 2010, when the law was working its way through the Democratic Congress. The unanimous opposition by Republicans was futile, but they managed to insert a provision that requires members of Congress and their staffs to obtain their employment-connected health insurance through one of the exchanges set up under the act.

That meant those 15,000 people could no longer participate in the federal employee health care plan most had been enrolled in. A typical workplace system, that plan paid about 75 percent of the cost of health insurance — a benefit worth an average of $5,000 for individual coverage.

Under ACA rules, the federal government, as a large employer, effectively could not contribute to the cost of insurance purchased through an ACA exchange offering individual and family coverage plans. The federal Office of Personnel Management instead directed the congressional employees to the ACA small-business exchange operated by the District of Columbia. Under ACA small-business regulations, an employer can pay a share of the employees’ premiums, thus preserving the benefit. The House and Senate duly filed paperwork in 2013 with the D.C. small-business exchange, and thousands of employees enrolled.

But there’s a problem with that: Neither the House nor the Senate comes close to qualifying as a small business under either the ACA’s definition, which limits the category to enterprises with 100 employees or fewer, nor the D.C. exchange’s own rule, which sets the cap at 50.

Vitter repeatedly attacked the congressional arrangement during the 2013-14 Congress, filing bills and amendments to overturn it. But his efforts went nowhere in the Senate, which was controlled by Democrats then (Republicans held the majority in the House).

The 2015-16 Congress took office in January with Republican majorities in both House and Senate. And in March, Vitter won approval by the full Senate of a measure to end the arrangement, but that was in an amendment to a budget plan that is nonbinding.

Meanwhile, a conservative legal group had filed a lawsuit over the arrangement, bringing forth copies of the House and Senate applications to enroll in the D.C. small-business exchange. They are riddled with what might charitably be called misrepresentations, many of them duplicated on each form: that the workforce in each case numbers 45; that the applicant is a state or local government; and that the payroll includes employees with the names “first last” and “Twenty Congress.” The applications were signed by whomever submitted them, but the signatures were blacked out in the documents released to the legal group.

The new Republican majority put Vitter in the chair of the Senate Small Business and Entrepreneurship Committee, and in an effort to find out who submitted the fraudulent applications, he fired off letters to the House and Senate administrations and the D.C. small-business exchange, which basically either ignored or stonewalled him. Undeterred, Vitter sought a committee subpoena in April for the unredacted documents: In a stunning setback, five senators from the committee’s Republican majority joined its Democratic minority to reject his request on a 14-5 vote.

Vitter has now issued a 36-page report recapping the five-year history of the affair. In his telling, it is a sorry tale, replete with closed-door meetings, clandestine negotiations, shadowy conspiracies and actions that are “unfair, illegal and secretive.”

Vitter is quite likely right about how it all went down. That may benefit him in his run for governor this fall, when he can campaign as a scourge of corruption, malfeasance and official privilege. It doesn’t appear, though, that virtue will help him prevail in his quest against those who make the rules in Congress. Should Vitter win the governor’s race and resign from the Senate, there are no doubt some among his congressional colleagues who will be glad to see him go.

Gregory Roberts is chief of The Advocate Washington bureau. His email address is groberts@theadvocate.com, and he is on Twitter, @GregRobertsDC. For more coverage of national government and politics, follow The Advocate Politics Blog at http://blogs.theadvocate.com/politicsblog/