One year after Chinese hackers exposed sensitive information from the personnel files of 22 million federal workers, contractors and others, the agency in charge of the response has no permanent leader.

In the 11 months since she has led the Office of Personnel Management, a heretofore obscure agency that vaulted to the headlines last June, Beth F. Cobert has only been acting director. Not because the Obama administration or anyone on Capitol Hill believes her unqualified for the job, a charge many leveled at her predecessor, whose weak response to the data breach forced her resignation. Cobert, with a long management resume in and out of government, is widely respected by lawmakers in both parties.

But her nomination by President Obama to be permanent director has been blocked for months by one Republican senator waging a tenacious campaign against a provision of the Affordable Care Act for legislative staff that Cobert had nothing to do with.

Louisiana Republican Sen. David Vitter doesn’t like Obamacare. He particularly doesn’t like Congress’s decision to keep federal health-care subsidies for lawmakers and their staffs the law was supposed to scrap.

To register his objections, Vitter placed a hold on Cobert’s confirmation vote by the full Senate after the Homeland Security and Governmental Affairs Committee approved her nomination 17 weeks ago with bipartisan support.

”I will maintain my hold on Beth Cobert to become director of OPM until we have corrected this outrageous act of fraud, whether legislatively or administratively,” Vitter said in a statement.

But on Thursday the four Senate Democrats representing Virginia and Maryland, home to hundreds of thousands of federal workers, asked Majority Leader Mitch McConnell (R-Ky.) in a letter to break the hold and bring Cobert’s nomination to the Senate floor.

Time is running out: With only a few weeks left until Congress breaks in July to campaign, the nomination could languish. Cobert’s term would technically end when Obama leaves office in January, but Democrats hope she might stay on if Hillary Clinton is elected.

The senators noted that OPM has a full plate that Cobert is deftly handling, from addressing “the serious consequences of the security breaches” to fixing a long-flawed hiring system, a stubborn backlog in retirement applications and transferring the government’s massive background investigation system to the Defense Department.

“Given the scope and magnitude of these challenges, it is unfortunate that one member of the Senate has continued to hold Ms. Cobert’s nomination for ideological reasons completely unrelated to her qualifications and performance,” Sens. Mark R. Warner (Va.,) Tim Kaine (Va.), Barbara A. Mikulski (Md.) and Benjamin L. Cardin (Md.) wrote to McConnell.

“While we understand our colleague has concerns…that occurred well prior to Ms. Cobert’s tenure at OPM, we continue to urge him to elevate those concerns in a productive and appropriate manner rather than hamstringing the agency at a moment when strong leadership is sorely needed.”

McConnell spokesman Don Stewart said in an email that he does not “have any scheduling announcements at this time” on Cobert’s nomination.

But a Vitter aide said the senator welcomes a floor vote, as long as he gets the chance to speak on his effort to kill a federal health-care subsidy worth several thousand dollars to lawmakers and their staffs.

Vitter has, since 2013, investigated how members of Congress and their aides became eligible to enroll in the District of Columbia’s small business health insurance exchange, which allows them to continue to receive a government contribution to their premiums under their previous health plans.

Last year Vitter tried unsuccessfully to subpoena the D.C. government for documents showing which congressional employees signed off on Congress’ application to the exchange. Cobert has said that OPM showed the documents to lawmakers, but without letting them take notes or make copies.

Adding to the drama over her nomination is a recent recommendation by OPM’s inspector general that Cobert, a 29-year veteran of McKinsey & Co. who was deputy management director at the Office of Management, is now in the acting job illegally.

The inspector general said she is ineligible to remain in office while her nomination is pending before the Senate and any decisions she has made in the past three months are “void” because of a recent court decision in an obscure law called the Federal Vacancies Reform Act.

The White House disputes the inspector general’s ruling.