(AP) — Lexington Mayor Jim Gray filed to run for Rand Paul's U.S. Senate seat on Tuesday, giving Paul a viable challenger and complicating his bid for re-election as he lags in the polls in his presidential campaign. Gray, the wealthy former CEO of a construction company, made history in 2010 when he was elected Kentucky's first openly gay mayor. [...] he has wrangled the city's pension funds and signed an ordinance raising the local minimum wage to $10.10 an hour. Party leaders had planned for former auditor Adam Edelen, a dynamic speaker and seen as one of the state's future Democratic leaders, to begin putting pressure on Paul after the state elections in November.