If the City Council had retained all of its nine members, it would have made history by becoming the first in Cambridge history to be elected to three terms.

But newcomer Craig Kelley, in his second run for council, played spoiler, knocking off incumbent David Maher in a stunning upset he attributed to winning the vote of “soccer moms” and striking a nerve with people who are dissatisfied with the quality of education in Cambridge.

Kelley, a soccer coach himself, partied with about 20 of his core supporters after results were announced late Tuesday.

“We won!” he shouted, accepting congratulatory hugs from just about everyone in the room.

During his victory speech, Kelly warned his loyal followers that he may have to make decisions and cast votes they don’t like.

“I will sacrifice friendships if I think it’s the right thing to do,” he told them. “I may have to make compromises that you don’t like.”

But facing the people who worked so hard to put him on the council was “incredibly humbling,” he said. “You guys keep me honest.”

Supporters all said they trusted him and did not expect him to “sell out” their respective causes — such issues as compliance with the Americans with Disabilities Act, safer streets, traffic calming, dog parks and controlled development, to name a few.

But there was one issue that Kelley said galvanized his support, one message he got across that solidified his base and propelled his candidacy to victory: schools.

Kelley said many have even asked him why he didn’t run for School Committee, because his message was so close to that of the upset winners on that board, Patty Nolan and Luc Schuster.

As a councilor, though, he still gets to vote on an education budget. He said that, unless the schools superintendent can justify it, he will not vote for any budget that does not spend more money on classroom support services and less on administration.

There are “scores of excess bodies in the administration,” Kelly said, vowing to find out why they are necessary.

“I will be ready to work with the council and the School Committee on getting the answers to these questions,” Kelley said yesterday while clearing out his Porter Square campaign headquarters.

Kelley had some very outspoken gadflies at his victory party, singing his praises. But that doesn’t mean he is a radical or “loose cannon,” as some have speculated, Kelley said.

“People who consider me a loose cannon are wrong,” he said, before listing his credits, such as serving in the U.S. Marine Corps and as chairman of the North Cambridge Stabilization Committee. “You can’t do those things if you are a loose cannon.”

Kelley said he won’t know what he is going to do on the council until he starts working. He promised one thing, however, and that is not to vote for any councilor to be mayor who would seek higher office during the next two years.

He said he thought the council needed the continuity of a mayor who is in for the long haul.

As for getting along, he said he was already welcomed onto the council by Mayor Michael Sullivan, and Kelley is careful to be more politic than some of his supporters.

“I want to be careful I don’t say something I will regret later,” Kelley said. “But I probably will anyway.”