The latest polls I heard are that, at least in South Carolina, 35% of people support Trump and plan to vote for him. However, at least 35% of the people who plan to vote for someone else would support Trump if they dropped out. That would mean, in math terms, as the number of candidates approaches 1 (Trump) his support approaches 58%. If there really were one candidate, however, the support would theoretically be 100%.
There was a dry run for this situation and it was 2012. There were a number of front runners in 2012. Rick Santorum won Iowa. Newt Gingrich won South Carolina. The problem was that they were all not Mitt Romney. There was no unified resistance. The Tea Party, for example, was waiting for Sarah Palin. Without her endorsement or a clear choice from the Tea Party movement itself, the larger Not Romney contingent failed to materialized. Eventually, Romney just outlasted the rest.
In the land to the blind, the one-eyed man is king. Donald Trump stoop out from the day he announced. He didn’t have money concerns. He pushed an unyielding message on immigration. His name recognition is nearly universal. Anyone against the establishment who hoped to compete with him probably lost as soon as Sarah Palin endorsed Trump. If the race gets down to two people, I think person #2 edges out Trump. However, the longer the number of candidates exceeds 2, Donald Trump approaches the majority of the vote.