Only in exceptional circumstances are major splits caused by Primary election. What tends to happen is that Primaries act as a stimulus to healthy debate over what the party stands for, with candidates from all parts of the political spectrum engaging in a contest to define the party in line with the wishes of the electorate.  Candidates focus on themselves, while the party leaderships can still play the role of holistically overseeing proceedings to make sure that the focus still remains the general election and what happens after the ballots in the primary election have been counted. It is possible to have rigorous primary campaigns without there being major splits that harm the party’s performance in the general election (The performance of The Democratic Party in 1992 bears this out).  While there maybe an emphasis on candidacy and personality, it helps to form a clear of what the party stands for in the general elections, marking out a clear choice between the parties at election time.