The 2016 contender on Monday made his first campaign stop in South Carolina since the shooting.
O'Malley's call comes days after the Supreme Court legalized same-sex marriage.
Trump says decision to cut ties is "weak" and "foolish."
The network is severing its relationship over recent comments about immigrants.
"We're not Indian-Americans or African-Americans or Asian-Americans," he says.
Cruz accuses Rove of questioning George H.W. Bush's judgment.
Dave Hamrick worked for then-Sen. Barack Obama's presidential campaign.
Cruz said justices don't believe views in America's heartland deserve to be respected.
Beau Biden reportedly urged his father to run in the months before his death.
The GOP candidate is ending his silence over the Supreme Court’s same-sex marriage decision.