There are a couple of ways you can customize the widgets on the campaign page. If you’re fairly comfortable with writing code & WordPress (or you have a developer on your team), you can create a custom template for your campaigns by creating a template file called single-campaign.php in your theme or child theme. You could copy and paste the contents of single.php into this and then modify it to use a custom widget area.
If you’re not too sure how to do all that, a really easy way to have custom widgets on campaign pages is to use a plugin that allows you to customize where widgets are displayed:
These plugins allow you to set certain widgets to show on certain content types (i.e. some only on posts, some only on campaigns).