The number of campaigns that can be published depends on your subscription plan. Here are the details:
FREE accounts: Up to 2 Published Articles
Starter accounts ($39.97/mo.): Up to 30 Published Articles
Pro accounts (99.97/mo.): Up to 100 Published Campaigns
Max accounts (199.97/mo.): Up to 300 Published Campaigns
Even though there's a limit on how many articles can be published, you can create as many draft campaigns as you like. It will only count towards your campaign limit once they are published.