“Lean to the green” is advice sometimes given to politicians, meaning that a politician should tend to take the side of where the money (green dollars) is coming from. The “lean to the green” saying has been in use since at least 1993, when representative Leslie Byrne (D-Va.; 1993-1995) remembered hearing it told to her.
         
 
6 June 1999, Washington (DC) Post, “Congestion: Find relief at The ballot box…,” pg. B8: 
When members of legislative committees that write land-use laws say, “Lean to the green,” they are referring to developer checks, not to environmentalists’ concerns.
 
SCL—The IT Law Community
Published: 01/05/2008
Lawrence Lessig’s SCL Lecture
(...)
One of the elements that underpins the argument is the considerable evidence that supports the view that government decision makers are either stupid or corrupt. Not blatantly corrupt in a Third World bribe way but ready to do what one US politician was advised to do - ‘lean to the green’, ie towards the source of campaign funds.
   
Virginia Pundit
Monday, June 29, 2009
The fault, Horatio, lies not in our politicians but in our selves
The Center of Public Integrity doesn’t think Virginia’s legislators have much.
(...)
During roll call votes in the House of Delegates, you’ll often hear joking exhortations to “lean to the green.” It’s more than a joke. The side with the most “green” wins more often than not.
   
Google Books
Republic, Lost:
How Money Corrupts Congress—and a Plan to Stop It
By Lawrence Lessig
New York, NY: Twelve (Hachette Book Group)
2011
Pg. 148: 
The best illustration of this dynamic is a comment from former representative Leslie Byrne (D-Va.; 1993-1995), recounting what she was told by a colleague when she first came to Washington. “I remember the comment of a well-known big money-raising state delegate from Virginia. He said, ‘Lean to the green,’ and he wasn’t an environmentalist.”
 
The Rachel Maddow Show (MSNBC)
(October 7, 2011 show, about 3:35 in this segment.)
LAWRENCE LESSIG: Leslie Byrne, a Democrat from Virginia, describes that when she went to Congress she was told, “always lean to the green.” And then to clarify, she continued, he was not an environmentalist.