GM who made the campaign needs to demote himself to player

I am the GM of a campaign, but am sharing this title with others. I want to play in their game as a player - however I can't find any way to demote myself down to player level (being the GM who started the entire campaign), and if I go into a campaign with the person I promoted to GM, it still lists me as a GM and I get GM control of everything. Is there any way for me to play as a non-GM without someone having to create a new campaign? Sorry if this question has been asked before, and thanks for any help you can provide!

I don't believe you can, but you can re-login as a player once you're in the game.

Ah okay then we'll make a new campaign. Thanks for your help!

Stephen R , HoneyBadger is correct that you can't demote the person who originally made the campaign  However, a GM CAN go to the settings tab on the sidebar and choose to re-login as a player.  Any GM controls you have will be removed and you will only see what a payer would see.

To add to what HoneyBadger and Sarah are saying, the GM can set up a Welcome starting page and move the player ribbon to that page. That way, when you log into the game you wont see anything while you are switching to player mode. Then he can move the players (including you) to the appropriate page. - Gauss

To add to everyone elses chime ins. This is one of the ways that various multiple GM games use. When they switch GM's they move the player's ribbon to the welcome page and the campaign creator knows that he has to change to player when entering the game board. This lets the new GM set his stuff up without people knowing about it. The original creator needs to keep his tabs on chat or settings till he rejoins as a players. It is an extra step or two but as others pointed out, you can have multiple GM's in one board. This is very useful when the original creator is a mentor or supporter and the whole campaign gets the bennies of that. 

Thanks everyone you've been really helpful! I'll keep what you've said in mind.