Campaign Online Forms and Lead Tracking

We have created online forms for our website that are associated with Campaigns.  Customers enter certain information in the form: company name, first name, last name, job title, phone number, email, etc. in order to receive a whitepaper download.

For a new customer the result is creation of both a lead (entity) and contact record, and tracking of a campaign response at the lead level.

Our existing customers will also use these online forms, so the form is setup to use duplicate detection criteria to merge into the existing record.  In most cases there are multiple contacts at the customer, but even though we have required entry of first/last name on the online form, we can not figure out a way to track the campaign response through to contact, so that the sales rep can follow-up with the particular person who downloaded the whitepaper.