I have many supporters of various candidates point out that the caucases and primaries held to date are not representative of the nation as a whole. Further, I have heard many state the vast majority of delegates have not been rewarded yet so all of the candidates should stay in and compete.
I am not going to argue the later point, but I would say that primaries and caucases held to date are representative of the nation. Take a look at Dave Leip's excellent Election Results site at http://www.uselectionatlas.org/USPRESIDENT/index.html. At the bottom of the page is a map of the US with the states that have already their caucases or elections. Looks fairly representative to me.