An unprecedented fight over who should sit on the board of ExxonMobil is turning into a referendum on chief executive Darren Woods as a decades-long struggle by climate campaigners comes to a head. Activist investor Engine No. 1 LLC wants to replace one-third of ExxonMobil's board in an effort to force the Western world's largest oil explorer to embrace a transition away from fossil fuels and end a decade of what it calls "value destruction." Shareholders are set to gather — virtually — for their annual meeting on May 26. The stakes are high. Under Exxon's bylaws, a victory for any dissident director would mean an incumbent must step down, equating to a zero-sum proxy contest: of 16 candidates, only 12 will prevail. Any dilution of Woods's influence over the board could derail his long-term plans and force strategic and tactical changes he has previously rejected.