Well the Constitution did fail to prevent the tyranny we are now experiencing, I mean it sounds great but the government doesn't adhere to it and hasn't for a long long time. I wouldn't say it's to blame though. I don't know how a new one would do any better because pieces of paper can't change the basics. Power corrupts and governments always want more power.  
In the words of Lysander Spooner 
"But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist."