spin doctor

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A person who publicizes favorable interpretations of the words and actions of a public figure, especially a politician.

from the GNU version of the Collaborative International Dictionary of English.

• noun a spokesperson for a political party or candidate who tries to forestall negative publicity.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A person employed to gloss over a poor public image (or present it in a better light) in business and politics, especially after unfavourable results have been achieved. A lobbyist; PR person.
• verb To generate spin (favourable interpretation or bias).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a public relations person who tries to forestall negative publicity by publicizing a favorable interpretation of the words or actions of a company or political party or famous person