America Rising PAC sent in several FOIA requests for Sanders' correspondence.
He accused Rubio of not standing with him when there was a chance to defund the abortion provider.
The ad features Jamiel Shaw, whose 17-year-old son was killed by an illegal immigrant.
Tickets for the event are going for $125.
The billionaire businessman leads the GOP field with 34.5 percent.
Amy Lindsay said she is still considering voting for the Texas senator.
The Dallas Morning News said Cruz "threatens to take the Republican Party to a dark place."
He was the only major candidate who didn't qualify for Saturday's GOP debate.
The Tampa Bay Times calls Sanders's proposals "expensive fantasies."
But Cuban said he makes a bigger difference as a private entrepreneur.