FRANKFORT, Ky. (AP) — The Kentucky Coal Association is warning Democratic U.S. Senate candidate Alison Lundergan Grimes against taking donations from a California billionaire known for environmental activism.Grimes attended a meeting in Chicago on Tuesday with major Democratic donors. She is seeking the nomination to run against Republican incumbent Mitch McConnell in the fall.The donors included NextGen Climate Action President Tom Steyer, who has pledged to work against candidates in favor of coal production in the United States.Association President Bill Bissett said anyone accepting donations from Tom Steyer or his group NextGen Climate Action will signal that candidate is against the production and use of Kentucky coal.Grimes has said many times she supports the Kentucky coal industry. State and federal campaign records show Steyer and his group have not contributed money to any Kentucky political candidates for the 2014 election cycle.