WASHINGTON, D.C. — U.S. Sen. Bill Nelson, entering his final days representing Florida, on Wednesday delivered his final speech on the Senate floor.

Nelson lost to Florida Gov. Rick Scott in a hotly-contested race that wasn't decided until Nelson conceded days after the Nov. 6 election.

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  • Sen. Marco Rubio called Nelson champion for space program

Nelson won his first Senate election in 2000, defeating U.S. Rep. Bill McCollum.

The 76-year-old Democrat spent about 30 minutes recounting moments during his time in D.C., from the contentious but important debate on the Affordable Care Act, to rewriting the blueprint for the space program, to helping constituents fight through the bureaucracy to get results. 

"It's our fellow citizens, the teachers, the soldiers, the factory workers, the moms, the dads, the students, the farmers, those are the ones that have inspired me to dedicate a life to public service," Nelson said. "And those folks have been my strength."

Nelson started his political career in the Florida legislature in the 1970s. From there he served in Congress -- this is when he also flew on the space shuttle, becoming the first congressman in space. In the 90s he served as Florida treasurer. 

"The journey has been a joy," Nelson said. "I leave this Senate today filled with hope for the future and the fondest memories.

"I admit it is hard to leave the friends and the work that I love."

But Nelson also talked about the failures -- the fact, for instance, that Congress has not passed a budget in 18 years, or the pushback on campaign finance reform. 

Nelson gave advice to colleagues who will serve in Congress after he leaves office. 

"Resist the pulls of partisan acrimony and the forces that seek to divide us. Tribalism is what drives us apart and it will take us down."

Sen. Marco Rubio, in talking about Nelson, said there has "been no greater champion for the space program."

"His leaving the Senate will be a tremendous loss and will require us to work harder," Rubio said.