Hi,
This depends on your CRM integration.
We use SFDC for sales, so a lead that goes to a sales rep goes to SFDC via a specific campaign (linkedIn, app note etc.,)
If this lead gets synced again to sales then that specific campaign gets attriputed to that lead in addition to the first one and the sales rep gets notified for each campaign attribution.
This way a lead can go to sales and after a while the sales rep will get another notification for him telling him that this lead is interested again.
If you are using just Hubspot than this procedure can probably done via custom properties or objects.
Hope this helps