We plan to send an email campaign to unresponsive prospects to determine if they're still interested in our service, went with another service, or other options.
The options are links in an email. They click a link, a custom field is filled with their choice and their sales rep is alerted.
When it comes to the "other service" option, they get a Marketo landing page with a one-question form to select the other service they chose (or none of the above). I'd like to track the email click (not everyone will fill out the form) but then override that selection with the selection from their form. With an email click, the custom field is filled with "No-other service." With a form fill, that could change to "No-CompetitorA" or "No-CompetitorB," etc.
Can I do this in the same campaign? Or would I need separate campaigns?
You don't need a campaign at all for the form. The Filled Out Form activity itself results in a change to the data value (unless you've blocked updates).
You don't need a campaign to change (overwrite) the data value, which was the topic of your post.