A Senate committee on Wednesday narrowly backed President Donald Trump's nominee to serve as the next NASA chief.Republicans on the Senate Commerce, Science and Transportation Committee used their slender majority to overcome objections from Democrats to advance the selection of Rep. Jim Bridenstine, R-Okla. The party-line vote was 14-13.Bridenstine, 42, is serving his third term representing a conservative district in northeast Oklahoma. Democrats criticized past comments he made dismissive of global warming as a man-made problem. They also voiced concern about Bridenstine's harsh criticisms of Democratic lawmakers and fellow Republicans over the years, and questioned whether he would keep the space agency from being mired in political battles.Sen. Bill Nelson, D-Fla., said the job on NASA administrator is one of the most challenging positions in the federal government, and required a strong scientific and technical background. He said the next administrator "must not be political.""It is a position where failure of leadership quite literally means the difference between life and death," Nelson said.Bridenstine appeared before the committee last week and promised to run the space agency on a consensus agenda driven by science.