And to get to that convention, Trump has to do so well,even with all the other conservatives in the running, that he wins at least 8 primaries by more than 50%. If he wins at 49% and the other conservatives split 40% and Kasich and Bush share the remainder, Trump still loses vis a vis Bush and the RNC.
Most of the others will be gone by the NH primary. Even if they are still in it they will get such insignificant amounts of votes it won’t matter.