Recently, I go to know the term "Snollygoster". Kind of interesting. These term is used in USA to define "a politician who is not interested in helping his voters but is instead driven by personal gain of wealth".
Definition from www.worldwidewords.org
"A shrewd, unprincipled person, especially a politician."
Definition from www.thefreedictionary.com
"One, especially a politician, who is guided by personal advantage rather than by consistent, respectable principles."
Definition from www.dictionary.com
"a clever, unscrupulous person"
Interestingly, i cannot find this work in www.merriam-webster.com
Maybe it is not yet a proper word...