QUESTION:
Is there a way to run existing Leads through the current active assignment rule in DemandTools? I do not want to actually update any data in the Leads themselves, I just want to have the owner reassigned based on the assignment rule.
ANSWER:
Yes. In DemandTools Options there is a setting called "Use Default Lead/Case/Territory Assignment Rule". Check this box to trigger active assignment rules when inserting or updating records using DemandTools.
Once enabled the user can mimic an update to all the Leads that should be run through the assignment rule. This can be done via MassImpact by setting a field equal to itself using the 'field' tab, or MassEffect by exporting the desired Leads and then mapping back any field and processing an update.
If using MassImpact will need to check the "Update Unchanged Records" box in the results grid on screen 3 to force the update even though the data is physically NOT changing.
More information on DemandTools Options can be found here
NOTE: It is highly recommended that history tracking be turned on in Salesforce for the owner field when checking the option for "Use Default Lead/Case/Territory Assignment Rule".
The DemandTools restore files WILL NOT contain the previous owner information, since DemandTools is NOT physically updating the owner field. DemandTools is simply triggering an update which in turn triggers the assignment rule to fire in Salesforce. If the changes need to reversed for some reason, a report can be run from the Lead History table that shows the previous owner.