Boosting the group in June was a reported $10 million donation from casino mogul Sheldon Adelson. Adelson, who dumped more than $20 million into a group supporting Newt Gingrich's efforts in the Republican primary, committed to backing Romney's election in the spring after the former House Speaker's exit from the race.

Adelson's donation alone was more than what was brought in by Priorities USA — despite that group's best month to date. 

“Last month, we raised over $6 million, which is about $2 million more than we raised the month before, which was $2 million more than we'd raised the month before," Priorities USA Director Bill Burton told Bloomberg on Friday. 

Restore our Future will look to seize on that financial advantage later this month by running a sizable television campaign during the Summer Olympics in 11 swing states.