I came across the wonderful word snollygoster [ˈsnɒlɪˌɡɒstə] today. It is defined as follows:

– One, especially a politician, who is guided by personal advantage rather than by consistent, respectable principles.
– A politician who cares more for personal gain than serving the people (Slang, USA)

From: The Free Dictionary.

– A shrewd person not guided by principles, especially a politician

Etymology: from 19th-century American English. Possibly from snallygaster, a mythical beast that preys on poultry and children, possibly from the Pennsylvania German schnelle geeschter, from the German schnell (quick) and geist (spirit).

From: Wiktionary.

– a fellow who wants office, regardless of party, platform or principles, and who, whenever he wins, gets there by the sheer force of monumental talknophical assumnacy.
Columbus Dispatch, Ohio, 28 Oct. 1895

From: World Wide Words

It doesn’t seem to be used much any more, perhaps because it isn’t needed as there isn’t anybody who behaves like this, especially not politicians.

Here’s an interesting TED talk about this and other political vocabulary:

Are there any similar words in other languages?