After spending more than $100 million mostly on losing Republican election campaigns this year, casino billionaire Sheldon Adelson said he planned to stay in the game and double down on his political donations.

Mr. Adelson, who was one of the Republican Party's biggest donors in 2012, will again give heavily to GOP candidates and conservative causes, he said in an interview, especially to state-level, antiunion initiatives.

"I happen to be in a unique business where winning and losing is the basis of the entire business," said Mr. Adelson, who directly backed one winning and eight losing candidates in the ...