Lame duck

Etymology

The term began in 18th-century London’s stock exchange, describing a defaulting investor who “waddled out” unable to pay — a lame duck. It crossed to American politics by the mid-19th century for an officeholder serving out a term after losing or declining to seek reelection.

noun phrase · /laym duk/
An official still in office but with waning power because a successor has already been chosen.
What it names
The awkward interval when a leader still holds the title but has lost the leverage that made it matter.
Example
As a lame-duck president, he found Congress unwilling to take up his final proposals.
Related idea
A lame duck is weakened by imminent departure; an interregnum is the broader gap between one authority and the next, and a sinecure is the opposite — an office that carries pay but never carried real power.