TN Congressman -- GAFFE OF THE YEAR ... Sexual Assault Begins at Home

Prepare to apply palm to forehead.

Tennessee Congressman Steve Cohen made one of the all-time blunders yesterday when asked about a sexual assault case involving a Tennessee Titans football player.

The 65-year-old politician explained that he's not really a big football guy ... but keeps up with Peyton and Eli Manning ... and knows the following thing to be 100% true:

"Eli and Peyton DON'T DO sexual assault against people ... other than their wives."

(apply palm to forehead now)

Even more shocking, the congressman didn't seem to realize his gaffe ... and moved on to the next topic without correcting himself.