# David Costello Former deputy secretary of the Maryland Department of the Environment, running in the 2026 Democratic primary for U.S. Senate in Maine. Third-tier candidate polling well behind [[Janet Mills]] and [[Graham Platner]]. ## 2026 cycle Primary date: 2026-06-09. Running as a policy/environmental candidate without the institutional backing of Mills or the populist momentum of Platner. Biographical details NEEDS VERIFICATION — stub record only. See [[ME-Sen-2026]] for full race context. ## Related - [[ME-Sen-2026]]