I've copied the PHP code sample for creating a new campaign, and overall the process seems to work as intended.
However, I'm having trouble when copy/pasting my HTML template code into the editor box, and submitting it as an edited campaign - although it passes all of the values properly, when I look at the message in CC itself, all of the quote and double quote characters are preceeded by a slash - which then breaks the design.
How can I pass the HTML I've built into the new campaign, while preserving the characters?
If I understand you correctly, you would need to use html Entities. Can you please post an example of your post so I can see what we are working with?