“If you can’t take their money, drink their whiskey, screw their women, and vote against ‘em anyway, you don’t belong in the Legislature” is a quote by Molly Ivins (1944-2007) that’s often attributed to Texas politics. The saying was first used by Jesse Unruh (1922-1987) in California politics, cited in print from May 1961. Unruh was talking about lobbyist gifts.
   
There are some quotes below of a somewhat similar usage in Pennsylvania politics in the 1950s, but this is probably unrelated to Unruh’s famous use of the saying.
   
     
Wikipedia: Jesse M. Unruh
Jesse Marvin Unruh (September 30, 1922 – August 4, 1987), also known as Big Daddy Unruh, was a U.S. Democratic politician and California State Treasurer.
 
Born in Newton, Kansas, he served in the U.S. Navy during World War II. After leaving the Navy, Unruh enrolled at the University of Southern California, and received a B.A. in Political Science and Journalism in 1948.
(...)
Famous Quotes
“Money is the mother’s milk of politics.”
“If you can’t take their money, drink their liquor, fuck their women, and then come in here the next day and vote against them, you don’t belong here.”
     
About.com: Women’s History
Molly Ivins Quotes
From Jone Johnson Lewis
(...)
As they say around the Texas Legislature, if you can’t drink their whiskey, screw their women, take their money, and vote against ‘em anyway, you don’t belong in office. 
 
18 May 1957, Monessen (PA) Daily Independent, pg. 8, col. 5 ad:
DRINK THEIR BEER, CARRY THEIR SIGNS, AND TAKE THEIR MONEY, BUT VOTE FOR A “WATCH DOG” of City Spending by VOTING:
For Council
STEPHEN SINCHAK
 
18 May 1959, Monessen (PA) Daily Independent, pg. 1, col. 1 ad:
WHO’S being DUMPED? WHO’S the logical candidate to be picked up?
 
WHY haven’t they answered ALL my charges? WASN’T it the TRUTH? You can’t fool ALL the people ALL the time. Drink THEIR beer, carry THEIR signs and TAKE THEIR money, BUT VOTE for STEPHEN SINCHAK.
   
Time magazine
California: Big Daddy
Friday, May. 05, 1961
(...)
In 1954 he was elected to the assembly. Eying the swarm of free-spending Sacramento lobbyists, Unruh decided that they could be put to systematic practical use. He became a one-man collection agency, spreading the lobbyists’ largesse among deserving Democrats for their campaign chests. To cries that such practice is unethical, Unruh simply snorts: “If you can’t take what the lobbyists offer and still vote against them, you don’t belong here.”
 
Google Books
The California governmental process: problems and issues
By Eugene C. Lee and Willis D. Hawley
Boston, MA: Little, Brown
1966
Pg. 73:
One hard-bitten answer often voiced among professional politicians in Sacramento, our state capital, runs like this, “If you can’t take the lobbyists’ money, eat their food, drink their booze, and vote against them — you don’t belong here.”
   
Google Books
Crisis in Car Insurance
By Robert E. Keeton, Jeffrey O’Connell, John H. McCord, University of Illinois at Urbana-Champaign. College of Law
Urbana, IL: Illinois University Press
1968
Pg. 234:
“If you can’t drink their booze, eat their food, take their contributions, and vote against them, you don’t belong here.”
     
Google Books
Ronnie and Jesse: A Political Odyssey
by Lou Cannon
Garden City, NY: Doubleday
1969
Pg. 101:
“If you can’t eat their food, drink their booze, screw their women and then vote against them, you have no business being up here,” Unruh would say. 
 
Google Books
The Pacific States of America:
People, Politics, and Power in the Five Pacific Basin States
by Neil R. Peirce
New York, NY: W. W. Norton
1972
Pg. 35:
In those early years, Unruh uttered two harsh dicta still remembered: “Money is the mother’s milk of politics,” and, speaking of lobbyists, ” If you can’t take their money, drink their booze, screw their women, and look them in the eye and vote against them, you don’t belong here.”
 
14 February 1977, Long Beach (CA) Independent, pg. A4, col. 1:
Back in the 1960s, Unruh, then Democratic speaker of the California Assembly, commented on how legislators in Sacramento should handle lobbyists.
 
“If you can’t eat their food, drink their booze, s—w their women and then vote against them, you have no business being up here,” Unruh said.
   
Google Books
Nothin’ But Good Times Ahead
By Molly Ivins
New York, NY: Random House
1993
Pg. 204:
The definitive statement on Texas political ethics—source unknown, but often quoted by Texas liberals—is: “If you can’t take their money, drink their whiskey, screw their women, and vote against ‘em anyway, you don’t belong in the Legislature.”