WASHINGTON — President Trump's choice to run NASA faced blistering broadsides at his confirmation hearing Wednesday from Democrats who questioned whether his past skepticism of climate change, his condemnation of LGBTQ protections, and his criticism of fellow lawmakers made him unfit to lead the space agency.

FILE - In this Feb. 28, 2016, file photo, Rep. Jim Bridenstine, R-Tulsa, speaks in Tulsa, Okla. President Donald Trump’s choice to head NASA faces a contentious Senate confirmation over his past comments dismissive of global warming as a man-made problem.

Five years as a conservative Republican representing eastern Oklahoma have given critics plenty of ammunition against three-term congressman Jim Bridenstine. And Democrats on the Commerce, Science and Transportation Committee were not shy about aiming their fire at the NASA nominee.

Florida Sen. Bill Nelson, the top Democrat on the panel and a leading congressional proponent of the space program, led the charge against Bridenstine.

Not only were his past comments on key policy positions such as global warming and same sex marriage troubling, he told Bridenstine, but his public criticisms of more moderate Republicans suggested an inability to lead an agency dependent on collaboration.

"Your recent public service career has not instilled the confidence about your leadership or ability to bring people together," Nelson said. "Unity is so important in NASA ...Your record and your behavior in Congress has been divisive and it's been extreme as any we have seen in Washington."

Bridenstine sought to allay concerns that he would not respect the work done by NASA or bend to an ideological curve. He pledged to "build on the work" of the Obama administration and pursue "a consensus agenda driven by science and based on national interests."

He also touted partnerships with Democrats on space-related initiatives,especially on weather forecasting improvements and an expanded role for private companies operating in Earth's orbit.

"When it comes to space issues and when it comes to issues that are important to the national security of this country, I have worked across the aisle," he told the committee.

If the Senate confirms the 42-year-old former Navy flier, he would be the first elected politician to hold a job that’s generally been the purview of scientists, engineers and astronauts.

Bridenstine, who sits on the House Science, Space and Technology and the Armed Services committees, doesn’t have a formal science background. His last job before being elected to represent Oklahoma’s 1st District in 2012 was as executive director of the Tulsa Air and Space Museum & Planetarium.

Sen. Bill Nelson, D-Fl.

A low-key member of Congress serving his third term, the Rice University graduate has won praise for his work advancing the interests of the emerging commercial space industry.

NASA employs about 18,000 workers and has an annual budget of roughly $19 billion. It's primarily charged with conducting space exploration missions, developing supersonic aircraft, and launching satellites that measure changes in Earth's climate and ocean temperatures.

Committee chair Sen. John Thune, R-S.D., supports Bridenstine's nomination and said he believes the congressman will secure enough votes to win confirmation in the Republican-controlled Senate. A vote in committee could come as early as next week to forward the nomination to the full Senate.

Democrats on the committee went after Bridenstine’s dismissal of climate change and its link to human activity during a floor speech in 2013.

“Global temperatures stopped rising 10 years ago,” Bridenstine said four years ago, refuting the overwhelming conclusion of the scientific community. “Global temperature changes, when they exist, correlate with sun output and ocean cycles.”

He was more circumspect during Wednesday's hearing, telling Sen. Brian Schatz, D-Hawaii.,  he believes carbon dioxide is a greenhouse gas and that humans contributed to carbon dioxide in the atmosphere. But he stopped short of agreeing with the broad scientific consensus that humans were the primary cause of global warming, saying "we're just scratching the surface" on determining the extent.

And while he didn't retreat from his conservative values like his stance against same-sex marriage, Bridenstine told the committee he would not seek to impose his "personal" views on NASA's inclusive culture.

"I absolutely believe that every human being has value (and) they will be treated fairly," he said.

Bridenstine also downplayed differences with fellow Republicans, saying past statements he's made against Florida GOP Sen. Marco Rubio and House Speaker Paul Ryan, were uttered in the heat of the 2016 presidential campaign and would have no bearing on his job running NASA.

Bridenstine appeared in ads on behalf of Texas GOP Sen. Ted Cruz that suggested Rubio, then a candidate for the White House, was soft on terror because the Florida senator had supported immigration reform.

Bridenstine last year also slammed Ryan on Twitter for abandoning Trump after the release of an Access Hollywood tape where the then-presidential candidate is heard making demeaning statements toward  women.

Rubio, who will be voting on Bridenstine's nomination if it reaches the floor, has expressed reservations about the NASA nominee.

“NASA is at a critical juncture in history, and it is important that its mission remain free of politics and partisanship," he said at the time of Bridenstine's nomination in September.

Cruz, who sits on the Senate Commerce, Science and Transportation Committee, criticized the Democrat's handling of the hearing as a "sorry performance" that could have lasting ramifications.

"If the confirmation ends up going down as a party-line vote, I think that would be deeply unfortunate for NASA and the space community," he told Bridenstine who flew combat missions in Iraq and Afghanistan. "I hope we see Democrats courageous enough to recognize your extraordinary record of service and personal integrity."