The pledge was delivered by the casino mogul's aide, Andy Abboud, during David and Carl Koch's donor summit this week in suburban San Diego and was among the biggest pledges made there, Politico reported Friday.
The summit also featured the announcement of the Grassroots Institute, a new candidate training academy supported by the conservative billionaire brothers.
Politico said the Grassroots Institute adds a new tool to a coalition of Koch-backed groups, including Americans for Prosperity, among the biggest spenders on anti-President Obama ads.
Groups in the Koch network said they collectively would spend nearly $400 million in the run-up to the 2012 election, making the brothers key players in a planned $1 billion campaign by GOP-allied third parties, Politico said.
Adelson, whose family is among the top donors to political groups, committed earlier this month to donating $10 million to a super PAC supporting Mitt Romney, Obama's presumptive GOP challenger.