How were the leaders chosen to rule the roman republic?

In the days of the republic, government officials were elected and most could select their own assistants. They were usually men from prominent families, either of the wrong age to run for public office on their own, or a politically connected family. In the days of the principate, the major officials were appointed, and generally the officials could select their own working partners, but there were times when the emperor appointed assistants as well. Many times an official was appointed on the basis of who he knew, not on what he knew.