I know nothing about politics at this level. I wonder if several candidates or their staffers had conference calls to discuss this.
"Supporting us will take votes from Trump way more than from you."
"It's hard for us to give you money even if it costs us a single vote."
"It may be a net gain in votes for you if it undermines Trump, but either way, we'll be in your debt."
"Are you saying you'll make Cruz your VP candidate if you get the nomination?"
"It's early yet to talk about that. Maybe that will happen. This would be just an informal alliance that we'll maintain as long as it keeps making sense to both of us."
"Okay. We'll do $500k for now and re-evaluate in a month. "

I have no idea if works that way or if the "back-room" deals are more sinister.

They're trying to do two things:
1) Keep a business woman in the race to steal Trump's thunder
2) Keep Carly far enough away so as not to be a threat, but close enough to be named as VP for the women's vote.

Good move...especially if it works.