You can use the Person is created trigger, with the following filter conditions -
Original Lead Source is Empty
Lead Source Most Recent is not Empty
Original Lead Source is not Empty
Lead Source Most Recent is Empty
Filter Logic - (1 and 2) or (3 and 4)
In the flow, you'd want to pull 2 Change Data Value flow steps -
Campaign Flow -
Flow Step 1
Change Data Value - Choice Step 1
if Lead Source Most Recent is not empty, update Original Lead Source = {{lead.Lead Source Most Recent}}
Default Choice - Do nothing.
Flow Step 2
Change Data Value - Choice Step 1
if Original Lead Source is not empty, update Lead Source Most Recent = {{lead.Original Lead Source}}
Default Choice - Do nothing.
The SL of the campaign will only allow new people created having data in only one of the field, i.e., people with data in both the fields or no data in either fields will be filtered out by the campaign SL.
Before activating a data management trigger campaign, in most cases it is recommended to run a batch campaign to process/append data to the existing people, this is done via one time batch campaign.
Let us know if you have any questions.
... View more