According to the Associated Press, Adelson previously contributed $10 million to Restore Our Future, the super PAC backs presidential candidate Mitt Romney and has donated $5 million each to two organizations promoting House Republicans.
During the Republican primary he and his family backed former House Speaker Newt Gingrich - donating some $21 million to a super PAC promoting the candidate which enabled him to keep his campaign afloat - the AP wrote.
Brothers Charles and David Koch are billionaire executives at Koch Industries who founded the small-government, anti-tax group Americans for Prosperity.
According to POLITICO, personal-investment businessman Charles Schwab, also made a major "seven-figure donation" to the Koch summit.
POLITICO reported Americans for Prosperity was among the biggest spenders on tough ads attacking President Barack Obama, and Kochs's Themis, a voter mobilization database, reportedly played a role in the Wisconsin recall fight among other groups.