This seems so basic but not finding anything. Please help.
SFDC Campaign member records are similar to being a program member in Marketo. These are a different object than the Marketo lead and SFDC Lead/Contact record. You can create custom fields on the Campaign Member record in SFDC and you can use those as Constraints in the Member of SFDC Campaign filter. If there is a particular value you want to add in a custom field on your lead record, you'll need to create a smart campaign that recognizes when that custom field value is set and then changes the data value of the Marketo lead custom field.
Beth Hassett, Marketo has limited ability to write to the Campaign Member object outside of the fields that sync via Program/Campaign integration.
Instead, once the field is in SFDC, you should be able to use an SFDC workflow rule to write the value of that field to the Campaign Member object. This would be a really good way to get a snapshop of lead info associated with a point in time stored on the campaign member record.
To update a Campaign Member in Salesforce with data from Marketo it sounds like I need to add the matching field to the Contact/Lead and Campaign Member records and then use Salesforce Workflow or Process Builder to update the field on the Campaign Member.
Thank you both for your prompt replies and great ideas!!
Beth Hassett - exactly! The lead/contact field holds the most recent value, and then the campaign member can contain a snapshot as of a particular event (e.g., the moment of success/responded in the campaign).
Is this still the case or is there an update?
You might want to check this out too: Handling Multi-Select Fields from Salesforce in Marketo