The "Make America's Military Great Again" event will be aired live from Los Angeles.
Donald Trump asserted that Rick Perry is “getting out of the race.”
Responding to Trump's pledge, Bush noted that he has "Voted Republican since 1972."
Poll results show why it was so important for Republicans to have him sign the pledge.
"I don't think you want a nominee [who] offends whole areas of the public, whole ethnic groups," Paul said.
He said illegal immigrants are being used as a "punching bag" in the race.
The super-PAC plans a $16.25 million ad blitz to help Walker's lagging support.
Trump said he will not change his mind about the pledge.
Captain Crunch leads PPP's survey of "joke candidates."
It is only Clinton's third sit-down interview of the 2016 cycle.