Like the Contract with America before it, the pledge may succeed in driving votes.

FORBES: The GOP Pledge: Smaller Government, Bigger Deficits

The site says the pledge is a "moral commitment" not a "legal contract".

BBC: US billionaires pledge 50% of their wealth to charity

The pledge is a moral commitment to give, not a legal contract, and it does not involve pooling money or supporting a particular set of causes or organizations.

FORBES: Ten More Tycoons Sign Buffett And Gates Giving Pledge: Dalio, Kinder, DeJoria