Have always though Newt was the pick, but he is getting up there in age. I just can't see Republicans being thrilled with men from NY and NJ as their President and VP. IMO, Christie has always been the Attorney General pick. Ernst is very interesting but Trump has said all along he wanted someone with Washington experience to help him navigate those waters. She is very new to Washington. However, female, very bright, War Veteran, list goes on. From all accounts, a much better pick than Palin was for McCain. Haley may have had a shot until she talked crap about Trump. Pense has always been my wildcard. Supposably a very bright guy, but has an insider rep which goes against Trump's calling card.
All said and done, he needs someone who can say the right things and be very smart on the campaign trail. Christie is a ticking time bomb (much like Trump). Never know what he will say. Newt is very calculated and has a negative history that the Dems will attack. JMO, in this election someone like Ernst would help Trump immensely. Extremely likeable, great campaigner, intelligent, war veteran, midwestern values, etc. She checks off several boxes for him. Women, Veterans, Evangelicals, etc. Two of those segments he has done well with so far, but to get the women vote is critical for him.