I see what you did there...lumping all the others together instead of listing how many Trump has versus each other candidate, individually.
Yes, because this primary is basically Trump vs. an alternative to Trump. Trump has his 30% or so, but all the people who do not want Trump are divided among all the others. As the field narrows, the latter will become more concentrated on one or two. The only problem is if that will be too late, and we end up with essentially a plurality nominee.