A new judge (Peyton Turner) asked me an interesting question and I did not know an answer to it. If you have some time, I would like to know what you think happens:

My board state is: Chromatic sphere, lots of land, Forbidden Crypt, Lich's Mirror, with no cards in my graveyard.

I cast demonic tutor, and while that is resolving announce that I am casting Panglacial Wurm from my library.

Because I am a jerk I decide to pay for the Panglacial Wurm starting with chromatic sphere. The Chromatic Sphere draw effect is replaced with getting a card from the graveyard, which is replaced with losing the game, which is replaced with Lich's Mirrors trigger.

I now have an announced Panglacial Wurm, with 1 mana in my mana pool as well as a demonic tutor on the stack. What happens, as I do not have the mana to pay for Panglacial Wurm?