 The constitutional history of the Roman Republic can be divided into five phases . The first phase began with the revolution which overthrew the Roman Kingdom in 510 BC , and the final phase ended with the revolution which overthrew the Roman Republic , and thus created the Roman Empire , in 27 BC . Throughout the history of the republic , the constitutional evolution was driven by the struggle between the aristocracy ( the " Patricians " ) and the ordinary citizens ( the " Plebeians " ) . Approximately two centuries after the founding of the republic , the Plebeians attained , in theory at least , equality with the Patricians . In practice , however , the plight of the average Plebeian remained unchanged . This set the stage for the civil wars of the 1st century BC , and Rome 's transformation into a formal empire . 
