How do political parties achieve their aim?

Political parties do the bidding of those who pay for them. They often need to get people to vote for them in which case they try to get votes so they can hold power and put in the laws those funding them desire.

It has always been that to some extent but in the past political parties were often created by the people to address issues of inequality or to advance a political belief. That is the history of the NDP, a Western based party meant to advance the causes of Western Canadians. Something they are clearly far from today as they hold many anti-Western Canadian beliefs but beliefs well supported by those that fund them today.