Dr. Jackson, a rear admiral in the Navy who serves as the White House physician, was already expected to face difficult questioning during his testimony before the committee. Last month, Mr. Trump fired his first Veterans Affairs secretary, David J. Shulkin, an experienced hospital administrator and veteran of the V.A. medical system, and then chose Dr. Jackson largely out of personal affinity.
The White House did little or no vetting of his background before announcing his nomination on Twitter. Before serving as a White House physician, Dr. Jackson had deployed as an emergency medicine physician to Taqaddum, Iraq, during the Iraq war.
The Senate only received paperwork from the Trump administration formalizing Dr. Jackson’s nomination last week.
Committee Democrats met briefly Monday evening to discuss how to proceed. Mr. Tester is leading the investigation. Mr. Tester met with Mr. Isakson Tuesday morning shortly after announcing the postponement.
The White House defended Dr. Jackson’s record in a statement, but did not address the nature of the claims against him.
“Admiral Jackson has been on the front lines of deadly combat and saved the lives of many others in service to this country. He’s served as the physician to three Presidents — Republican and Democrat — and been praised by them all,” said Hogan Gidley, a deputy White House press secretary. “Admiral Jackson’s record of strong, decisive leadership is exactly what’s needed at the V.A. to ensure our veterans receive the benefits they deserve.”
Lawmakers were already preparing to press Dr. Jackson on his views on the role of private medical care for veterans, instead of the department’s government-run health care system. Senators planned to challenge his lack of management experience running a large organization. The department is the federal government’s second largest, employing more than 370,000 people and operating sprawling health and veterans benefits systems.
Before his nomination, Dr. Jackson had garnered little public attention and his policy views were unknown. He took a rare turn in the spotlight in January, when he appeared on national television to announce the results of Mr. Trump’s first physical while in office. At the time, there was speculation over the president’s physical and mental health, and Dr. Jackson offered effusive compliments on both. Mr. Trump was pleased with the performance.
“I’ve found no reason whatsoever to think the president has any issues whatsoever with his thought processes,” Dr. Jackson said. At one point, he even quipped that given Mr. Trump’s genetics, he might live to 200 years old if he had a healthier diet.
Mr. Trump fired his first Veterans Affairs secretary amid deep ideological disagreements over privatization of care at the department and extended fallout from a scathing report by its inspector general about a trip that Mr. Shulkin had taken last year to Britain and Denmark. Mr. Shulkin, a politically moderate physician and former hospital executive, remained well-liked on Capitol Hill and among veterans groups, who felt he was a pragmatic leader who understood the department intimately.