Portland’s elected mayor has had a rough year, and so has the elected mayor form of government.

Mayor Michael Brennan has had to weather direct attacks from a sitting governor, staff turnover and biting criticism from his colleagues on the City Council. Some of that criticism has carried over to the city charter itself, which created the mayor’s office without giving it many specific powers. Some argue that the office should be made “stronger” with the power to hire and fire employees, while others say the city was better off when the council selected a ceremonial mayor from among its members.

But before you can judge Brennan’s performance or evaluate the makeup of the office, you have to account for an important missing piece of the puzzle at City Hall. The city’s charter anticipated that the mayor would be the political leader representing a citywide majority of voters teaming up with a strong city manager who would be the top administrator.

What the charter commission did not anticipate was when the first mayor took office he would not be paired with the kind of strong manager Portland had become used to over the previous 30 years.

The puzzle will be fully assembled Monday, when the council is expected to hire Jon Jennings as city manager.

Jennings has a unique resume for a city administrator. He is currently a South Portland assistant city manager, but he has also worked in business, most recently as co-owner of the Maine Red Claws, where he was instrumental in brining the franchise to Maine and leading the effort to build an arena as part of a mixed-use development at Thompson’s Point.

Jennings has other impressive resume points, including a degree in public policy from Harvard and stints as a staffer in the Clinton White House and as an assistant coach for the Larry Bird-era Boston Celtics. He has experience on big stages dealing with big egos. He will need it.

The city charter is very clear on the manager’s responsibilities. He hires most of the department heads and supervises all city operations. He reports to the City Council, but he has to be strong enough to protect city staff from micromanagement by elected officials, including councilors and the mayor.

The mayor and council are supposed to set policy and the administration is supposed to carry it out. It takes strong leadership on both sides of that divide to make sure that the city can effectively respond to residents and businesses that demand representation and services.

With Jennings in place at City Hall, the charter approved by voters in 2010 will finally get a chance to operate.