It's called "campaigning".
It is the main activity involved in running for public office.
It is essentially like any other marketing campaign, but for a political candidate asking for a vote, instead of for a good or service, urging you to purchase it.
Generally speaking, they have to do so either through advertising or earned media coverage. At the end of the day, political parties - while closely regulated in many respects - are entirely responsible for their own conduct and internal policies.
In the scholarship, it's not even entirely clear where the line between party-as-social-identity, and party-as-...