President Obama has nominated a new chief to oversee the government's major healthcare programs.

The president has picked Andy Slavitt to head up the Centers for Medicare and Medicaid Services, the federal agency that runs the massive health insurance programs for the elderly, disabled and poor, the White House announced Thursday.

Slavitt has been filling in as acting CMS administrator ever since former administrator Marilyn Tavenner resigned earlier this year. Before joining the government in 2014, he was a top official at Optum, a division of UnitedHealth Group that helped fix healthcare.gov where Americans can buy Obamacare health plans.

Besides running Medicare and Medicaid, CMS is deeply involved in running many parts of Obamacare, including delivering insurance subsidies to poor and mid-income Americans.

Slavitt would have to be confirmed by the Senate, where Republicans eye him with some suspicion, particularly for his role in assisting healthcare law implementation. Majority Leader Mitch McConnell said Slavitt's nomination will receive "thorough consideration in the Senate," but said "no one can successfully manage a law as unworkable as Obamacare."

Orin Hatch, top Republican at the powerful Finance Committee, said Slavitt will need to answer "tough questions" about his former employer and its relationship to CMS.

"Mr. Slavitt's conflicted history in the medical services industry has produced mixed results and raised a number of serious concerns," Hatch said in a statement. "As such, he will be expected to demonstrate that he is up to the challenge and capable of successfully leading the agency through the monumental tasks that lie ahead."