Reversing his steadfast anticasino position, Holyoke Mayor Alex B. Morse plans to announce on Monday that he supports a proposal to develop a gambling resort in his economically struggling city, intensifying the battle for the most sought-after casino license in the state.

“I think we’re all realizing that casinos are coming to Western Mass., and Holyoke cannot sit on the sidelines,” Morse said in an interview to discuss his stunning pivot on the issue.