The growing protest movement against U.S. oil and gas pipelines has so far focused on stopping or delaying new construction, with some high-profile successes. Now, in Michigan, a broad coalition of opponents is entering a new frontier: Pushing to rip out and reroute an existing pipeline – Enbridge Inc.’s aging Line 5, which crosses the Straits of Mackinac. They fear the pipeline will leak into the Great Lakes, which contain about a fifth of the world’s fresh water and sustain the state’s second- and third-largest industries, agriculture and tourism. Those concerns – which are shared by two likely candidates for governor – also have far-reaching implications for energy firms […]