The Cambridge Election Commission announced nine unofficial City Council winners near midnight Tuesday, but the then-uncounted 22 percent of the votes may overturn those preliminary results.

The unofficial announcement predicted that seven of the nine incumbents would retain their seats, with the other two spots going to Edward J. Sullivan and Leland Cheung, a student at Harvard Kennedy School and the MIT Sloan School of Management.

But the final tally remains far from certain.

Election commissioners labored Wednesday to hand-count an unusually high number of ballots that could not be processed electronically—thanks to the write-in campaign of five-time City Councillor Marjorie C. Decker, who failed in September to complete her paperwork to be placed on the ballot.

Usually only a couple hundred ballots cannot be processed electronically because they contain a vote for a write-in candidate, a stray mark, or some other error, according to City Council candidate Thomas Stohlman, Jr.—but this year’s commissioners must hand-count 3,590 such ballots.

Decker—who may yet secure a sixth term on the Council—waged an aggressive campaign Tuesday to make her candidacy known. Campaign workers maintained a presence at almost all polling sites on Tuesday, distributing stickers with Decker’s name for voters to affix to their ballots, according to Decker’s campaign manager Jeni M. Wheeler.

“If we win, that’s what will have made us win,” Wheeler said. “We feel very good.”

Cheung, Sullivan, and current Vice Mayor Sam Seidel are the likeliest to not succeed, since they are the three preliminary winners who received the fewest votes.

“It’s absolutely razor-thin,” said Cheung, while adding that he is “cautiously optimistic” about gaining a spot on the Council.

The three candidates declared elected on the first count—incumbents Timothy J. Toomey, Jr., Henrietta Davis, and current Cambridge Mayor E. Denise Simmons—are the likeliest to officially emerge victorious.

Aside from Decker, the only incumbent not listed among preliminary winners was Larry W. Ward, who joined the Council in Feb. 2009 after Brian P. Murphy ’86-’87 resigned his seat. He garnered the most votes out of the 12 unofficially defeated candidates.

“Only the top 3 to 6 of these [preliminary winners] have a lock on the election,” wrote local political aficionado Robert Winters on his Web site, the Cambridge Civic Journal.

He added that it would be “foolish” to assume before all the ballots are tallied that Cheung, Sullivan, and Seidel have in fact won.