I can give my opinion, and some won't like it, but it is honest. Everyone has a rearend, including me, so I will show mine-)
As long as the race was heavily domestic, Trump and Carson had the advantage. When looking at the Democrats, Bernie would also show much stronger.
But, as soon as a good chunk goes foreign policy, Carson, Trump, Fiorina along with Bernie, lose a lot of luster. Weighting of foreign policy ranges from little, to a bunch, depending upon the voter. The more problems there is across the world, the more the foreign policy weight pushes against domestic policy concern. What we are seeing is a re-alignment of power in the GOP primary, mostly because OF foreign policy.
It is obvious that Trump nor Carson have foreign policy experience, although by lefty standards that should NOT handicap them, since Obama had no experience at foreign policy either, or anything else for that matter.
Conservatives are more pragmatic than Democrats though. The strength of Trump today comes from those he has stolen from the Democrats. They are as much into the populist message as everyone else is. But, if foreign policy continues down this road, eventually pragmatism will come to the forefront.
The only question then will be.................if Trump supports Cruz as he takes the lead, will the Democrats who supported Trump follow suit!!!!!!