What is this ms_pid field I see in my .csv files?

An ms_pid (MarketSmart Personalized Identification), is the unique ID assigned to each of supporter record in your Dashboard. It’s what we use to create personalized URLs when we send emails on your behalf and how we pre-fill donor data in forms. The ms_pid data point being passed through your campaign data is part of our Open API update.You will need to include ms_pid as a new field in your CRM in order to match supporter data to your CRM.