"Except for" vs "Except In"

What is the difference between the following two?

• We didn't have a chance to meet, except for the campaign.
• We didn't have a chance to meet, except in the campaign [or "except for in the campaign"].

I would also appreciate if there is a better way of conveying the same message.

Assuming a correct comprehension of the semantics here, I think the problem is with the choice, or lack of choice, of preposition for "the campaign". I would use the following:

We didn't have a chance to meet; except for during the campaign.

The way I read it, both statements are correct depending on purpose. "For" conveys the purpose of participating in the campaign. "In" means place but not purpose; it could have been by chance.