Today is Election Day, with polls open from 7 a.m. to 8 p.m. and the vote count beginning in the Cambridge Senior Center, 806 Massachusetts Ave., Central Square, after polls close and the ballots from all 33 precincts arrive.

Although an initial ballot count should be done with a couple of hours of the polls closing, there will be no reliable election results for the City Council — there are 21 candidates running for nine seats — until Wednesday, when write-in ballots will be handled. Councillor Marjorie Decker, having missed an Election Commission filing deadline, is running for reelection as a write-in candidate and retains a serious chance of winning. (There is no similar complication for the School Committee race, which has nine candidates vying for six seats.) Overseas absentee ballots — if there are any — will be counted Nov. 13.

As it has since 1941, the city will be voting with proportional representation, in which voters rank their preferences instead of marking ballots for a single favored candidate.

The weather is expected to be partly cloudy and in the 50s, which won’t cause voters to stay away from polling places, but there are also no burning issues to draw them in. The city’s politics guru, Robert Winters, expects voter turnout to be similar to 2007, the most recent municipal elections, when about 24 percent of eligible voters filled out ballots. (At 59,237, the electorate is about 2,900 stronger than two years ago.)

On the other hand, “there are arguably six or seven interesting challengers this year,” Winters said. He cited “the Leland Cheung factor” as among the best chances to shake up results in which incumbents are otherwise expected to do well.

Cheung, 31, is a graduate student at Harvard’s Kennedy School of Government and the Massachusetts Institute of Technology’s Sloan School of Management. He wants the city and its universities to work better together, and to ensure students — about a fourth of the city’s population — are represented in city government.

An Oct. 7 story in The Harvard Crimson noted that “Cheung estimates that he will need to receive about 1,500 first-place votes to claim a seat—amounting to only about 5 percent of the 30,000 combined MIT and Harvard students,” and Cheung has been canvassing among students.

“He could bring out some voters from the college crowd who wouldn’t otherwise think about voting,” Winters said, and that’s what makes Cheung’s presence on the ballot such a wild card: Instead of running against other candidates, he’s bringing out his own unpredictable number of voters, very likely turning a nine-chair game of musical chairs into one with eight chairs.

The last such candidate was Matt DeBergalis, who graduated from MIT in 2000 and ran for the council three years later. He finished eighth, in part by registering voters at places no other candidate would go — the Man Ray nightclub, for instance. “He scared the daylights out of some incumbents,” Winters said, but once the distribution of votes peculiar to proportional representation began, DeBergalis was left behind in the count.