Delaware Gov. Ruth Ann Minner announced the appointment this afternoon.
Biden, who just won his seventh term in the Senate, must vacate his seat before being sworn in as Vice President on January 20th. Minner said Kaufman will be sworn in sometime in early or mid January.
Biden's son, Attorney General Beau Biden, had been seen as a possible replacement for his father. He announced last week that he wouldn't accept the appointment if offered, saying he planned to continue serving in the National Guard.
The [Wilmington] News Journal's Jeff Montgomery writes that "[t]he selection of the former Biden chief of staff was widely seen as a move by Vice president-elect Biden to protect his seat for" his son Beau, who is presently deploying to Iraq.
There will be an election in 2010 for Delaware voters to decide who will fill the final four years of Biden's term. Montgomery writes that the choice reflects a snubbing of Lt. Gov. John Carney; one Delaware professor suggests in the News Journal story that it will be viewed by some as "a backroom deal."