We have a couple thousand contacts from a CiviCRM database that already have a Minnesota State File ID.  However, when our Election Center import happened, it created new contacts with the same State File ID.

What fields does the import process use when determining if a duplicate already exists, other than something obvious like the NBEC guid?  We'd like to make sure the import process can match up as many as possible so that we don't have to spend a lot of time de-duping afterward.

For reference, one example of a duplicate state file ID in our system is 2291750.  There are two contacts with that ID that are clearly duplicates of each other (similar names, addresses, etc.), but the system doesn't seem to be able to catch that, either on the Dedupe page, the Duplicates button, or the "Possible duplicate" search field.

Thanks ahead of time for any pointers.