No, I think you pick the person who (1) has the best chance to implement an America first agenda if elected and (2) has the best potential to draw voters from the other side. So far, that seems to be DT on both points.
Sorry. I do not and have not argued that DT is the most philosophically conservative candidate running. Arguably that’s Teddy. My personal reservations about Teddy’s sincerity, ethics, eligibility, and motivation notwithstanding, he has the charisma of a wet mop. He’s also running as a staunch conservative where that point of view will win you maybe 20% of the population. It’s not a conservative country however much we might wish it to be. His ability to build a coalition beyond that 20% who would be inclined to support him offhand is seriously doubtful.
The polls show that Trump does not draw enough from the other side to even beat Cruz, let alone one of the D’s. Trump is drawing some support from Dems who are just looking at the universe of Republican candidates. Once the contest becomes Trump vs Sanders or Clinton, that crossover support evaporates.
A good example is the comments made by Jimmy Carter. He obviously did not endorse Trump, but he did say that he preferred Trump over Cruz. That would not carry over to the general.