A person or thing that isn't properly able to function, especially one that was previously proficient.
The description of 'lame duck' is often applied to politicians who are known to be in their final term of office, when colleagues and electors look toward a successor. It is also sometimes used to describe office-holders who have lost an election but have not yet left office.
In recent years (as of 2006) both George W. Bush and Tony Blair, unable to see out further electoral victories, have been faced with such mutterings, for example:
In May 2006, The Washington Post ran an article titled 'Bush's Political Capital Spent', including the opinion:
"Such weakness has unleashed the first mutterings of those dreaded second-term words, 'lame duck'."
In April 2006, The [London] Times ran an article titled:
"Is Blair a 'lame-duck' Prime Minister?"
US presidents have long suffered this fate, partly due to the electoral rules in America, which limit the number of terms that a president may serve, and the USA is where the phrase originates when applied to politicians. The Congressional Globe entry for 14 January 1863 has:
In no event could it be justly obnoxious to the charge of being a receptacle of ‘lame ducks’ or broken down politicians.
Historians now describe various 19th century US presidents as 'lame ducks'. The first such description of a US president I can find which was written while he was still in office isn't until 1926 though, and relates to Calvin Coolidge. The Wisconsin newspaper, the Appleton Post-Crescent ran a piece titled, 'Making a lame duck of Coolidge', in May 1926:
"... the voting in other Republican states should hinge pretty largely on the issue whether Mr. Coolidge shall be permitted to become a lame duck president for the final two years of his term."
The actual origin of the term is nothing to do with politics though and is quite specific in meaning. It comes from the London Stock Market and referred to investors who were unable to pay their debts. In Horace Walpole's Letters to Sir Horace Mann, 1761, we have:
"Do you know what a Bull, and a Bear, and a Lame Duck are?"
In 1771, David Garrick, in Prologue to Foote's Maid of Bath wrote:
"Change-Alley bankrupts waddle out lame ducks!"
In 1772, the Edinburgh Advertiser included:
"Yesterday being the settling day for India stock, the bulls had a balance to pay to the bears to the amount of 23 per cent. Only one lame duck waddled out of the alley, and that for no greater a sum than 20,000."
We are still familiar with the terms 'bull market' and 'bear market', referring to rising and falling markets respectively, but 'lame duck' in the specifically stock trading context is now little used.
Why should someone who has no assets be called a 'duck'? Could it be related to the cricketing term, 'out for a duck' - used when a batman is out without scoring any runs? It seems not. That term is much later and refers to the zero on the scoreboard being similar to a duck's egg. First used in 1867, in G. H. Selkirk's Guide to Cricket Grounds:
"If he makes one run he has 'broken his duck's egg'."
See other phrases that were coined in the USA.