Casino mogul gives $10M to pro-Romney super PAC

That's according to two officials familiar with Adelson's contribution. They confirmed earlier media reports and spoke on condition of anonymity because they were not authorized to discuss the matter.

The cash infusion to the Restore Our Future political action committee comes as Romney's own campaign is making its largest ad buy so far in the head-to-head contest with President Barack Obama. The Romney buy is worth about $3.3 million.

Romney's allies at Restore Our Future have been on the air for weeks as Romney's campaign raised money. The two groups can't legally coordinate their efforts, but outside groups working in Romney's favor are staffed with former aides familiar with the candidate's strategy.