In politics, an “honest man” is often described as someone (a politician or a voter) who, when bought, stays bought. A “dishonest man” is someone who sides with the person who buys him last.
 
Various people have been given credit for this saying; Simon Cameron (1799-1889) is often given credit, but no historical printed citations can confirm this. An 1884 source (below) credits Tom Ochiltree. The saying appears to date from the 1850s.
 
 
The Quotations Page
An honest politician is one who, when he is bought, will stay bought.
Simon Cameron
US financier & politician (1799 - 1889)
 
29 September 1856, New York (NY) Daily Times, “Buying up Pennsylvania,” pg. 4 col 3.
If they are to be bought up so cheaply they will not stay bought long enough, we imagine, to do any good to their purchasers.
     
5 December 1865, New York (NY) Times, pg. 4:
FRIENDS IN NEED.—HECKER’S radical organs began to hedge yesterday. His morning organ, leaving HECKER out of account, proceeded to adjure the electors to vote for the man they thought most likely to render faithful service to the city. The evening Hecker organ occupied itself with a defence of Mr. ROBERTS against the aspersions cast on hischaracter by Copperheads, and closed with the announcement that “the best experts predict confidently the election of Roberts.” This, we supposed, is what may be called backing one’s friends. POOR HECKER! Doubtless, he pays enough for friendship. But the trouble apparently is that his friends wont stay bought. He will go to bed to-night a wiser, if not a happier man.
   
8 September 1866, New York (NY) Times, “An Astonishing Display of Corruption,” pg. 4:
“I call a man honest,” said a New-Jersey politician, “who when he is bought, stays bought.” Most of these voters were “honest” within the New-Jersey definition.
 
20 October 1875, Inter Ocean (Chicago, IL), “Daniel Dougherty—He Delivers an Eloquent Lecture on American Politics,” pg. 8:
The politician sells himself over and over again, and it is a difficult matter to know when you have got him. The definition of an honest politician has been given as a man who will “sell himself and stay bought.”
 
19 September 1884, Kansas City (MO) Star, “Saving Broadwy,” pg. 2:
The New York aldermen are honest politicians according to the definition once given by TOM OCHILTREE. That is to say “when they are bought they stay bought.”
     
10 December 1884, Kansas City (MO) Evening Star, “Some Honest Politicians,” pg. 2:
They are an honest lot of politicians, those New York aldermen. According to a distinguished authority, an honest politician is one who, when he is once bought, stays bought.
 
18 June 1885, San Francisco (CA) Bulletin, pg. 2:
It has been given by a famous lobbyist as the definition of an honest official that he is “the rascal who will stay bought.” Even this is a standard of integrity not always obtainable.
   
23 January 1890, Worcester (MA) Daily Spy, ‘Standards of Honest,” pg. 4:
In an official inquiry into certain election frauds in New York some years ago, one of the witnesses, having used the phrase “an honest man,” was asked to define it. “Well,” said he, “I should say—an honest man—is one—who will stay bought.”
 
3 February 1891, Daily Nevada State Journal (Reno, NV), pg. 3, col. 1:
The Chronicle says a Carson lobbyist’s idea of an honest legislator is “one who will stay bought.”
 
23 September 1892, Reno (NV) Evening Gazette, pg. 3, col. 2:
Nevada lobbyists want none but honest men elected to the Legislature this fall—that is, men when they buy them once will stay bought.
   
6 February 1893, Janesville (WI) Gazette, pg. 4, col. 2:
A local politician defines “an honest man” as one who can be bought and who stays bought.
 
Google Books
If Christ Came to Chicago!
By William T. Stead
Chicago, IL: Laird & Lee
1894
Pg. 184:
Boodlers, according to the dealers in boodle, are divided into two categories, the honest and the dishonest boodlers. The honest boodler is the Alderman who, when bought, “stays bought,” and does not sell out to the other side; the dishonest boodler is perfectly willing to take money from both sides and dispose of his vote, not according to the first bid, but the last.
   
18 July 1894, New York (NY) Times, pg. 4:
The House conferrees have found these dealers in concessions as firm as the everlasting rocks, answering to that description of the honest man who says that he is the man “who will stay bought.”
 
Google Books
The Leg-Pullers;
Or, Politics As She Is Applied
A tale of the Puritan Commonwealth by one who has been there (E. B. Callender—ed.)
Boston, MA: Pemberton Square Publishing Co.
1895
Pg. 8:
In politics an “honest” man is one who will stay bought; an “approachable” man is one who entertains no special channel for the receipt of customs, but may be offered financial consideration by anybody.
       
25 March 1896, New York (NY) Times, “‘Band-Wagon’ Campaign,” pg. 1:
If there is anything at all in the political adago that “the honest man is the man who stays bought,” it does not find any application at Republican National Conventions. The bought delegate pretty nearly always will vote for the man who buys him last.
     
30 January 1897, Daily Huronite (Huron, SD), pg. 2, col. 1:
The editor of the Howard Press is evidently an honest man, according to Ben Hoover’s definition at least, which is that an honest man is one who stays bought.
 
8 February 1898, Daily Oklahoman, pg. 3:
SUNDAY-SCHOOL Teacher.—What is your definition of an honest man, Johnnie? Johnnie (whose father is a First Ward politician)—A man who stays bought when he’s bought.—Philadelphia Record.