Voters are flocking to the polls today in chilly, bright weather to cast ballots in a preliminary election that will winnow the field of 12 mayoral candidates to two hopefuls who will face off in a final election on Nov. 5.

The election is the first wide-open mayoral race in a generation because of the decision by long-time Mayor Thomas M. Menino — still in love with the job and the city but beset in recent years by various ailments — not to seek a sixth term.

With Menino no longer dominating the political scene, the candidates have scrambled onto the stage. They’ve campaigned tirelessly for months, speaking at forums on such issues as charter schools, affortable housing, and transportation, and personally meeting thousands of voters. They’ve released TV ads and plastered the city with signs.

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The candidates are: City Councilor At-Large Felix G. Arroyo; non-profit executive John F. Barros; radio station general manager Charles L. Clemons Jr.; Suffolk District Attorney Daniel F. Conley; City Councilor-At-Large John R. Connolly; City Councilor Rob Consalvo; former city housing chief Charlotte Golar Richie; City Councilor Michael P. Ross; Codman Square Health Center founder Bill Walczak; State Representative Martin J. Walsh; former teacher David James Wyatt; and City Councilor Charles C. Yancey.

The Globe has reported that experts say that the outcome of the contest is difficult to predict. Several recent polls have found Connolly leading the pack. Other strong contenders, according to the polls, include Richie, Conley, and Walsh.

But political observers say that none of the candidates has had a break-through moment that captured the imagination of masses of voters and that the race is likely to come down to a house-by-house fight in which 20,000 to 25,000 votes could earn someone a spot in the final.

For the most part, the mayoral candidates have been civil to each other, reflecting the work they’ve done together in the past on various issues. Some commentators have praised the tone of the race.

Also on today’s ballot, 19 candidates are running for the City Council’s four citywide seats — a field that includes former council members, well-known community leaders, and political newcomers and that will be narrowed to eight finalists

The polls will be open today from 7 a.m. to 8 p.m. To find your polling place, click here.

For extensive coverage of the race from the Globe, including profiles and positions of the candidates on a wide range of issues, check out boston.com and bostonglobe.com.