If confirmed, Oz would run an agency that helps interpret and enforce many of the federal laws that shape employer-sponsored health plans and supplemental benefits programs, including the Affordable Care Act, the Mental Health Parity and Addiction Equity Act and the Health Insurance Portability and Accountability Act. He also would oversee Medicare and Medicaid.

Oz is a cardiothoracic surgeon who was a full professor at Columbia University's medical school. He later became better known as the host of television medical talk shows that mixed sober segments with segments about alternative medicine concepts, such as the idea of using green coffee beans to try to treat obesity.

Three of the Republicans on the Senate Finance Committee — Sen. John Barrasso, R-Wyo.; Sen. Bill Cassidy, R-La.; and Sen. Roger Marshall, R-Kan. — are medical doctors, and all of them voted for Oz.

Oz seemed to win respect from at least some Democrats on the Senate Finance Committee during a March 14 hearing. He found common ground by agreeing on the need to streamline the procedures health plans use to review requests for coverage and to reduce the amount of Medicare Advantage program spending going toward marketing and distribution costs.

Related: Dr. Oz addresses concerns, discusses prior authorizations, at CMS confirmation hearing

But, when the nomination came up for a vote, Democrats on the committee said they believe Oz refused to give clear answers about matters such as what he would do to defend Medicaid funding or implement federal nursing home staffing standards.

Sen. Ron Wyden, D-Ore., the highest-ranking Democrat on the committee, recalled that Oz had described the question about nursing home staffing as a complicated question.

"Quite frankly, I find that answer offensive," Wyden said. "It isn't complicated for the rest of us whether nursing homes ought to have adequate staff to take your mom to the bathroom or give your grandpa his meals."

Oz "also failed to provide basic factual responses to my written questions submitted after his hearing," Wyden said.

Wyden objected to reports that Oz had used a tax rule that lets at least some partners at partnership-owned companies avoid paying Social Security and Medicare payroll taxes.

"Nurses and firefighters pay these taxes out of every single hard-earned paycheck," Wyden said. "But the multi-millionaire nominated to run Medicare can't be bothered to do the same."

The Senate already has approved the nominations of three other top-level Trump administration benefits regulators. Scott Bessent is the Treasury secretary, Lori Chavez-DeRemer is the Labor secretary and Robert F. Kennedy Jr. is the secretary at the department that oversees CMS, the U.S. Department of Health and Human Services.

Senate committees have not yet scheduled hearings on the nominations of Billy Long to be the Internal Revenue Service commissioner and Daniel Aronowitz to be the assistant Labor secretary in charge of the Employee Benefits Security Administration.