Really? I always get my companions being fine with it, since it's not 'failing' it's the giver cancelling.
But yes, to the OP, The Marshal will only call a campaign when he has a task to accomplish, e.g. raid some villages, capture a town, generally fight the enemy until everyone is out of men e.t.c... The moment that objective is compeleted, he will call an end to the campaign, and any campaign quests you've been issued will be cancelled (or completed if you're curerntly on 'follow the army')