Spangenberg, 47, beat past "Jeopardy!" (search) champs Shane Whitlock and Grace Veach — and took home another $34,399.
"[Whitlock] was much quicker on the buzzer and it was very frustrating to be in that position of knowing the answer but just not getting in on time," Spangenberg told The Post.
Spangenberg's victory puts him in the "Super Six" of past "Jeopardy!" Champs — two of whom will try to unseat Jennings beginning Monday, May 23.
Jennings, a software developer from Salt Lake City, set a "Jeopardy!" record last year when he won over $2.5 million during a 74-game blitz.
Spangenberg pulled out his victory last night by correctly answering the "Final Jeopardy" question.
"I was substantially behind and really had to go for it and hope for the best," he said.
"When you're in a position like that, you have to have all your strategy planned."
Spangenberg, a 19-year NYPD veteran, is currently in Cambridge, Mass., where he's completing a master's in Public Education at Harvard University's Kennedy School.
The Ultimate Tournament of Champions continues Thursday night at 7 p.m. EDT.