History is on the ballot in Boston on Tuesday with voters set to choose a woman as mayor, but the state's top elections official expects that turnout will lag behind previous contests amid what he perceives as a lack of "intensity."

On the eve of Election Day in 61 Massachusetts communities, Secretary of State William Galvin told reporters he estimates 135,000 ballots will be cast in Boston, where voters will decide an open mayoral race and several contested City Council seats.

If Galvin's projection holds true, turnout among the city's 442,000-plus registered voters would land at about 30.5 percent, lagging behind three of the four most recent Boston municipal elections where the mayor's office was up for grabs.

One of the two finalists, Michelle Wu or Annissa Essaibi George, is poised to become the first woman elected to serve as mayor in Boston's history after Acting Mayor Kim Janey in March became the city's first-ever female mayor.

Despite those circumstances, Galvin said he believes the contest so far has not generated enough heat to warrant a more robust turnout prediction.

"I don't think the intensity is in this race as we've seen in some prior races," Galvin said. "For whatever reason, I guess no one is terribly frightened by the prospect of either finalist becoming mayor or terribly excited. That'll be the true measure of the turnout: how excited they are."

A turnout rate of 30.5 percent would be the second-lowest in a Boston election with the mayor's office on the ballot since 2005, the furthest back that the city's elections website posts data.

About 35.6 percent of registered voters cast ballots in 2005, followed by 31.2 percent in 2009, 38.2 percent in 2013, and 27.8 percent in 2017.

Tuesday's election is the first open mayoral contest in Boston since 2013, when former Mayor Martin Walsh defeated John Connolly by 4,889 votes. That race saw a total of 142,007 ballots cast, which would surpass Galvin's prediction for the current cycle in Boston even though the city had roughly 70,000 fewer registered voters at the time.

"I hope I'm wrong, but when I look at 2013, (the number) was 142,000 and that was a pretty intense race and a close race," Galvin said. "It's hard to understand that we'd go much beyond that."

Wu has led Essaibi George in pre-election polling and both candidates are working to turn out their supporters, as are city council candidates.

Voting by mail has had a "fairly robust" presence in Boston ahead of Election Day, Galvin said, with about 53,000 mail-in ballots requested and more than 38,000 received as of Monday morning.

"Bear in mind that some of these requests initiated in the preliminary election from voters who said they want to vote in every election this year, so I'm not sure that all of those ballots will in fact be returned," Galvin said. "But I'm still encouraged by the amount of ballots that have been returned already and will be returned today and tomorrow."

Statewide, 135,358 voters requested a mail-in ballot for a contest on Tuesday and 89,876 have returned their vote, according to data from Galvin's office. Rates of return vary by community, topped by an even 100 percent of the 102 ballots requested in New Bedford.

The lowest rate is in Springfield, where only about 31 percent of the 3,852 mail-in ballots sought have been received by elections officials. Galvin said that city is "a concern" because officials mailed ballots late after experiencing issues with printing.

Galvin stressed that any voters who received a mail-in ballot but have not yet sent it back should now return it in-person. Unlike last year, when any ballot postmarked by Election Day and received up to three days later got counted, ballots this time around must be received by 8 p.m. Tuesday.

NBC Boston on Saturday reported that Boston City Councilors Michael Flaherty and Ed Flynn alleged some mail-in ballots were undelivered and an unspecified amount were thrown out by a temporary postal worker.

Asked about the issue on Monday, Galvin responded that the allegations were "simply untrue."

"Boston was contacted by a candidate for City Council on Friday afternoon with a report. Boston tells us he came up with one person who was experiencing it, supposedly. The story about the temporary postal person -- we were obviously in no position to judge that," Galvin said. "We helped Boston reach out to officials at the Postal Service. The Postal Service went through it very carefully. They sent an email late Friday, both to Boston and we got a copy of it, saying all ballots have been delivered. They verified that by a subsequent statement today that the only mail that might have been disposed of was political mail, not ballots."

Galvin attributed a "slow count" of votes in the Boston preliminary election to 7,000 mail-in ballots that were placed in drop boxes or returned on the final day, which had to be cross-referenced to ensure those people had not already voted.

This time, Galvin said, he expects "a more orderly process."

City officials announced Friday they will upload unofficial results Tuesday night from each precinct that do not include any early voting and mail-in ballots centrally tabulated during the day at City Hall or that arrive on time but too late to be sent to a polling location for counting.

"The caution they exercised in the preliminary was well-placed. It was a relatively close preliminary election," Galvin said. "When you know that 7,000 ballots were received on Election Day and the difference between second and third was 3,000, you obviously had to be cautious. All of us take seriously the issue of protecting the integrity of the balloting, especially when so many are attacking vote-by-mail as something less than reliable."

New forms of voting such as mail-in ballots and expanded in-person early voting helped drive record turnout across the state in 2020, with the presidential and U.S. Senate races topping the ballot.

Those policies, implemented as temporary provisions during the pandemic, are set to expire on Dec. 15 without additional action from the Legislature.

Last month, the Senate approved legislation that would make expanded early voting and vote-by-mail permanent features. Top Democrats in the House, which earlier in the year tackled similar topics in a different format, have not yet said if they will take up the Senate's bill or pursue another short-term extension before formal lawmaking business for the year concludes Nov. 17.

Noting that deadline, Galvin said Monday that he is "very concerned about the future of vote-by-mail heading into 2022." He pointed to the Jan. 11 special Senate election, where voters in Revere, Winthrop, and parts of Boston and Cambridge will fill the seat vacated by former Sen. Joe Boncore.

Without action from lawmakers, "there would be no vote-by-mail available for that," Galvin said.

"Most of all, we have an excellent record using vote-by-mail," Galvin, a Democrat, said. "Last year's election in Massachusetts set turnout records across the board in all three events. Many, many voters of all parties found vote-by-mail a very attractive alternative. Everyone says they're for it, so hopefully, if everyone's for it, we'll get it done."