An alert Dorchester resident’s curiosity led to an unusual political discovery, after she found that her Adams Street housing complex was incorrectly assigned to District 3 instead of District 4.

The discrepancy has been acknowledged by city officials, who have taken steps in the last month to fix the error. Over 200 registered voters in the half block of Baker condominiums and apartments are now eligible to vote in the preliminary municipal elections on Tuesday, Sept. 8, according to Mayor Martin Walsh’s office.

In District 4, longtime incumbent Charles Yancey is defending his seat from challengers Andrea Campbell and Terrance Williams in a closely-watched race in an otherwise languid election season. Voters in District 4 and District 7 will be the only people going to the polls on Tuesday, since other district seats do not have enough candidates to necessitate a run-off.

After a candidate's forum Thursday, Yancey called the timing "highly suspicious," and suggested that the new District 4 voters be included in the next election rather than the current one.

Campbell seemed nonplussed by the influx of the new voters. "That's an Election Department issue," she told the Reporter, adding that the late timing is disadvantageous from a strategic perspective, as her staff could not incorporate the block into their door-knocking and outreach plan.

The discrepancy was identified by Terry Dolan, who has lived in the Baker Chocolate complex in Lower Mills for 24 years. It was not until a house party last month that it occurred to the generally politically-aware Dolan that there may be a mix-up in her voting district.

When a friend who lived nearby asked if she would be voting in the upcoming District 4 election, Dolan said she was surprised.

“No, we’re in District 3,” said Dolan, 67. As a member of the Ward 17 Democratic committee, Dolan said she was disappointed that she could not vote for Campbell.

The apartments — at 1231, 1241, 1243, 1245 and 1255 Adams Street — are located along a half-block in what was listed as Ward 17- Precinct 13, said Laura Oggeri, a spokeswoman for the Mayor’s office. A redistricting in 2012 kept Precinct 13 in District 3, but re-assigned Precinct 14 to District 4. But the Adams Street housing complex remained eligible to vote only in District 3.

However, Dolan’s curiosity had been piqued. A few days after the party, she looked up her voter registration with the Election Department — District 3. She then checked her address with the Neighborhood Services online search — and it came back as District 4.

Puzzled, she called the Election Department, which affirmed that her address was in District 3.

But now the retiree had sleuthing to do, and someone suggested she examine the old district maps.

“I was blowing up maps and looking and, sure enough, there’s a red line down Adams Street,” Dolan said.

She went back to the City with this information. They began looking into it on Aug. 11, Oggeri said, and Dolan's suspicions proved correct. The five addresses in Baker complex were indeed in Precinct 14.

According to the Boston Redevelopment Authority and the Election Department, they "had been incorrectly listed in the Street Book, dating back to at least 1999,” Oggeri said in an email.

To ensure that the 200-some voters in the Baker buildings would have the opportunity to register before the Aug. 19 deadline, City officials sent notices to affected residents explaining that they were actually in District 4. A registration drive took place at the complex on the 15th, during which Dolan estimated that about 10 new voters were registered, and continuing efforts were made to alert affected residents. The City' Mobile City Hall vehicle also registered voters on Aug. 17 and Aug. 18.

The City’s response was encouraging, Dolan said.

“They were very diligent, with a little bit of nudging, with looking into it,” she said.

The Secretary of State’s office is now reviewing the paperwork and will provide all relevant documentation, said spokesman Brian McNiff. He did not have an exact time when the review would be complete.

The mix-up did not have any substantive impact in election cycles prior to 2013, since precincts 17-13 and 17-14 were previously in the District 3 seat. (Both precincts vote at the same polling station, the Lower Mills Library on Richmond Street.) In 2013— in which the Baker residents should have received ballots for District 4— Yancey won re-election handily with 68.34 percent, clearing his only opponent— William— by 4,469 votes. In District 3, Frank Baker ran unopposed and won 97.76 percent of the votes.

Yancey, who disapproves of the immediate inclusion of what he estimates as 245 potential new voters, told the Reporter Thursday that "it almost sounds like political gamesmanship," and "I don't think it's appropriate to make a change as drastic as that in the middle of the election."

The shift of 200 potential voters either way could be more meaningful this year, as the District 4 race is the most closely-watched in the city. Still, Dolan said most of her conversations with other Baker residents have not demonstrated an overwhelming urge to vote having been otherwise disenfranchised.

Campbell and her staff point out that the apartment complex is a closed community in which they cannot door knock and leaflet. Dolan confirmed that leafletting is prohibited.

Essentially, “It was a good exercise in paying attention and speaking up if you have a question," she said. No one, Dolan said, should be unaware of an opportunity to vote.

(This story was updated Fri. Sept. 4 to include candidate reactions. -Ed.)