Good response by Tim Challies to the ridiculous “Blasphemy Challenge.” The unpardonable sin first requires a firm commitment to the deity of Jesus Christ.
“To commit this sin you must know that Jesus Christ is God and, despite that knowledge, ascribe the Spirit’s work through Him to the devil.”
[Here is the Nightline video and story covering the Blasphemy Challenge.]
Tony Reinke 
Since Jesus was warning the Pharisees about this, I have trouble believing that believing in His deity is a necessary condition to committing the sin.
This is clarified in the full Challies article. Blessings! Tony