I agree that it was not off the cuff. My sense is that for whatever reason, right or wrong, he doesn't respect her, and he is indifferent about getting her support. He didn't buy the reason she gave for not appearing at the rally. He may think she is weak on immigration.
Susana Martinez, the Yin to Donald Trump's Yang? - NBC News - Apr 25 2016
Following [self-proclaimed genius Bill] O'Reilly's comments the Governor's Press Secretary said she had no intention of entering the fray as a vice presidential candidate. Not surprising given Martinez endorsed fellow Latino Republican Marco Rubio and denounced Trump's comments about Mexican immigrants even leaving open the possibility that she wouldn't vote for him.
We don't know what happened behind the scenes either. He or the campaign may have had discussions urging her to appear, including discussions around her given reason. If she doesn't want to support him, using a pretext of prior engagements, his reaction is just a negotiating device. He's willing to walk away from the table. Is she?
I would like to know what has gone on behind the scenes because he has clearly concluded that there is value in attacking her. And the crowd response was supportive of his attack.
One thing I am finding is that every time I second guess Trump it seems he has a lot more in the background he has not put forward relating to almost everything he does.Vince Foster murder a perfect example.