Three years ago, Joe Rodriguez was an alder representing Fair Haven, bringing development projects to Grand Avenue, pushing foreclosure regulations and fighting for grant money for neighborhood nonprofits.

This is his first week back in City Hall — not as an alder but as a mayoral aide managing relations with the Board for the city’s first new leader in 20 years. Rodriguez, 27, replaces Michael Harris ’15 as Mayor Toni Harp’s legislative liaison.

The body of alders Harris has handed off to Rodriguez looks markedly different from the one he first faced at the beginning of the new term in January. From January to June, six alders, two in the same ward, resigned from the 30-member Board.

For some, the reasons were practical; “new opportunities” required Ward 3 Alder JeQueena Foreman to move outside the ward, she told constituents. Others vacated their seats for personal reasons. Ward 27 Alder Angela Russell gave little explanation for her exit, writing to Board leadership in April that she believed she could be more effective as a citizen than as a lawmaker.

The circumstances of Ward 19 Alder Mike Stratton’s withdrawal continue to reveal themselves, as he faces charges of assault and breach of peace surrounding a domestic dispute 11 days before his resignation.

But for half the alders who left their seats in the first six months of the term, a single calling drew them away: an appointment by the mayor to a position in her administration. First came a job for Jackie James, formerly of Ward 3, as deputy community services administrator. In the spring she became City Hall’s director of minority and small business initiatives, a position Harp created despite legislative pushback.

Doug Hausladen ’04 and Migdalia Castro also resigned from the Board in January in favor of director positions in the Department of Transportation, Traffic and Parking and the Elderly Services Department, respectively.

Hausladen said the Board remains vital to his work for the administration, which relies on the direct connection to residents only alders can maintain. He said his experience as a lawmaker also gives him perspective when talking about neighborhood issues.

“I know the feeling of getting 100 calls on any given item,” he said.

Harp’s chief of staff and a former Board of Alders president, Tomas Reyes, said the turnover underscores the collaborative approach the mayor has brought to bear on city governance. He said Harp first expressed reverence for the legislative process and pledged to be the Board’s partner during her campaign last fall. Harp, too, was an alder before running for state office.

Reverence went both ways. 18 alders signed a written statement last June pledging their support for the then-state senator and candidate. Board of Alders President Jorge Perez pointed to this early show of support as critical for bilateral relations between the legislative and executive branches.

“The majority of us supported her, and she saw some talent and skills in some of those people,” he said. She did not draw exclusively from the pool of alders who supported her. Hausladen, who did not back Harp, was among the alders who received a nod from the administration.

While some alders come and go, others remain. Chief among the long-lasting cohort is Perez, who has served on the Board for 27 years, across four mayoral administrations. He said uninterrupted service on the Board requires a stable employment situation since being an alder is a part-time job that pays just $2,000 a year.

Perez said the Board is well-served by having members with more experience who can show political newcomers the ropes.

“Nothing happens overnight in a legislative body,” he said. “You need a few years.”

Former mayoral candidate and two-term Ward 10 Alder Justin Elicker FES ’10 SOM ’10 said the imbalance of experience also creates an imbalance of power. Turnover, while it brings new voices into the political process, also inflates the power of those who stick around, he said.

Indeed the longer-serving alders are the ones with whom Rodriguez, who served two terms on the Board, said he already has relationships. One of his first tasks will be getting to know some of the newer faces, he said.

Rodriguez returns to City Hall having worked for several years as an “outreach organizer” for U.S. Sen. Richard Blumenthal LAW ’73.