Carry The Mail Meaning

(chiefly US, idiomatic) To work diligently; to serve as the principal performer of a demanding task or set of tasks.

Example: 1986 Jan. 8, Keith Schneider, "Agriculture Chief to Quit: Reagan Hails Block Tenure," New York Times (retrieved 5 March 2014):
  "My objective was to carry the mail for the President, working with the Congress, forging that new bill."
2011 April 12, Kent Wilson, "Sidney Crosby's historic season," (retrieved 5 March 2014):
  To say the Pittsburgh Penguins are a top-heavy club is an understatement. . . . The club is therefore completely reliant on Crosby and Co. to carry the mail up front.
2012 June 28, "Dallas Cowboys," Sports Illustrated (retrieved 5 March 2014):
  The coaches will say, "We have two starters at running back," but the guy who'll carry the mail is DeMarco Murray.