I'll admit that I'm not well versed in our own political process; definitely not as much as I should be. I have no idea how the Caucus affects the nominations other than usually if a candidate struts their stuff at the Caucus then they are more likely to get the nod of approval from their party. Once a party chooses a singular candidate it's pretty much unwritten (I believe) that the other sort of gracefully bow out and then support "the chosen one" in order that their party has a better chance of winning.

For instance, if Hillary wins the Democratic Caucus then all other Democratic candidates should bow out of the race slowly and gather up support for Hillary. Their support will hopefully "give" their would-be voters to the new "chosen one" so that the party as a whole can win the presidency.

That's my take on it anyway, please someone feel free to add or correct.