By Ned Parker and Joseph Ax RENO, Nev. (Reuters) -A slate of conspiracy theorists seeking to take over key U.S. election posts lost races in battleground states, after months of warnings from election experts and Democrats that their ascension could threaten American democracy itself. The final nail in the coffin arrived on Saturday in Nevada, where Republican Jim Marchant, who helped organize candidates under the “America First” banner, lost his bid to become the state’s top election official to Democrat Cisco Aguilar, Edison Research projected. Marchant and like-minded candidates echoed form…