PORT WASHINGTON, Wis. — A data center complex under construction here has become a flashpoint between city leaders who see a needed source of funding and nearby residents who oppose the project. The dispute is part of a growing backlash to data center construction across Wisconsin, and candidates for governor in both parties are adjusting their campaign messages as the midterms approach. Port Washington’s mayor has argued that the project will bring much-needed funding to the community. Neighbors, meanwhile, have strongly opposed the development. The competing priorities put a basic question before local officials: whether the financial benefits of a large private investment justify the costs residents believe they will bear. The complex was still under construction on Oct. 22. The available details do not specify its cost, projected tax revenue, job totals or the particular concerns driving neighboring residents’ opposition, making the promised community benefit and its local trade-offs central issues for residents and voters to scrutinize.