A shared interest in supporting Israel, fostered over 15 years, is at the heart of casino mogul Sheldon Adelson's support for Newt Gingrich's presidential bid.

It has been decades since America saw a wealthy patron become so identified with a presidential candidate. But Mr. Adelson and his wife, Miriam, account for a large share of the funding for an independent group supporting Mr. Gingrich's presidential bid, giving $5 million this week and $5 million earlier in January.

On...