Sen. Bill Nelson, the ranking member on the Senate Committee on Commerce, Science & Transportation and a former astronaut, derided Bridenstine for his past political rhetoric and opinions on climate change. The Florida Democrat suggested that these comments precluded Bridenstine from the position.
"As I have said, NASA is a family. This committee has heard me say many times NASA is not political. The leader of NASA should not be political. The leader of NASA should not be bipartisan; the leader of NASA should be nonpartisan. And when that has occurred when it has been partisan in the past, we've had a disaster," Nelson said in his opening remarks.
"Your recent public service career does not instill the confidence about your leadership skills or ability to bring people together. Unity is so important in NASA instead of division. What your record is ... your record and your behavior in Congress has been as divisive and extreme as any in Washington," he continued, citing to the Oklahoma Republican's criticisms of former President Barack Obama and Sen. Marco Rubio, his endorsement of Kelli Ward over Sen. John McCain in Arizona and his anti-LGBT platform, such as his 2013 opposition to same-sex marriage
"NASA represents the best of what we can do as a people. NASA is one of the last refuges from partisan politics. NASA needs a leader who will unite us, not divide us. Respectfully, Congressman Bridenstine, I think you've got a long way to go to prove to be that leader," Nelson concluded.
Bridenstine pushed back against the notion that his past political actions disqualified him.
"We have seen people from the political area do very well at NASA," he said, pointing to James Webb
, who served in the Truman administration before becoming administrator and under whom NASA successfully completed the Apollo moon landing.
"I want to make sure that NASA remains, as you said, apolitical, and I will do that to the utmost of my ability should I be confirmed," Bridenstine told Nelson during questioning.
Republican Utah Sen. Mike Lee defended Bridenstine, saying that "the fact that he's been willing to stand out is the reason I support this nominee."
"I cannot for the life of me understand why this would be something that disqualifies you," Lee said.
Bridenstine also came under fire for his past views on climate change and lack of background in science.
Speaking on the House floor in 2013, Bridenstine incorrectly said that global temperatures stopped rising 10 years earlier. In a 2016 interview with Aerospace America, Bridenstine argued that the climate is simply always changing. During his hearing, Bridenstine attested to the existence of climate change and humankind's role in it.
"I believe that carbon dioxide is a greenhouse gas. I believe that humans have contributed to carbon dioxide in the atmosphere," he said during his confirmation hearing. However, when pressed by Sen. Brian Schatz, Bridenstine would not say if humans were the primary contributors to climate change.
"It's gonna depend on a whole lot of factors. We're still learning more about that every day. In some years you could say absolutely. In other years during sun cycles and other things there are other contributing factors that would maybe have more than an impact," he answered. The current consensus, according to NASA
, is that "climate-warming trends over the past century are extremely likely due to human activities."
Bridenstine maintained throughout the hearing that science would drive his decisions as administrator. He noted in his opening statement that he intends to "build off the work done by the great people at NASA during the last administration."
Bridenstine graduated from Rice University with majors in economics, psychology and business and has an MBA from Cornell. After serving in the military, he worked as executive director of the Tulsa Air and Space Museum & Planetarium for four years.
The congressman has expressed a personal interest in space development. He introduced the American Space Renaissance Act in 2016, which would "permanently secure the United States of America as the pre-eminent spacefaring nation," according to a website for the bill.
Bridenstine is not commenting on the confirmation hearing, a spokesperson told CNN.