You say it was when Obama was elected. But here are a few other events that I've heard cited as finally killing the Constitution. (I've heard many other dates and events beyond those on this list.)
* The JFK assassination and LBJ's Civil Rights Bills.
* FDR's New Deal.
* The 1913 Federal Reserve Act.
* The Civil War.
* George Washington's suppression of the Whiskey Rebellion.
1861 after Lincoln assumed the Presidency.