A lobbyist is an activist usually paid by an interest group to promote their positions to legislatures. A lobbyist can also work to change public opinion through advertising campaigns or by influencing 'opinion leaders' or pundits, thereby creating a climate for the change his or her employer desires. The word lobbyist comes from the chambers in which the act of lobbying usually takes place, an anteroom near legislative bodies, for instance, or even the lobby of hotels where important people are staying. In American politics, most lobbyist organizations are headquartered on or near K Street in Washington DC, so "K Street" has become somewhat synonymous for lobbying.

It is very easy for a lobbyist to stray into bribery -- the most direct way to influence legislation, obviously, is to bribe enough law makers to ensure that the bill you support passes. Therefore, lobbying is heavily regulated. Of course, a lobbyist rarely makes the news unless he or she has transgressed the regulations, and as a result, 'lobbyist' has rather negative connotations these days. Measures to control the influence of lobbyists include campaign finance reforms, often promised but rarely passed.

When legislators lose re-election or choose not to run again for office, they often find a second career as a highly paid lobbyist, meeting with their former colleagues and touting the positions they are paid to promote. Of course, these are positions they supported while in office, so such jobs are not completely mercenary, yet they are widely considered an abuse of one's former position. This practice is, however, quite legal. Routinely, political scandals surface that have their roots in some lobbyist activity or other -- usually unlawfully large gifts to lawmakers, or quid pro quos of some form.