Unless he appoints him Secretary of State, Mike Pence is the best choice for Trump's VP. Pence was the best choice for Trump in that he did more than anyone else to ensure that Trump's Hostile Takeover of the GOP would take and not be rejected.
Fallin was the only female running mate that would have worked with Trump; she needed the job to continue her career. Ernst and Haley were too independent. Fallin, however, could not have added the gravitas to the ticket that Pence did.
In regards to Ernst, nah. I have a feeling that, if it came down to it, she'd be a Trump loyalist who'd give full-throated damnations of his opposition until the end.
