One thing that can't be argued with: whoever David Paterson picks to replace Hillary Clinton in the Senate will need win an election at the end of Clinton's term in 2010, and again in 2012.
The impending campaign in an expensive media market has been cited as a reason to pick, say, Caroline Kennedy, who has the connections and the fund-raising capacity to do it.
It's also been cited as a reason someone like Kennedy might not want the seat–the Times wondered if she would be interested in the "unglamorous aspects of campaigning across New York’s 62 counties."
While electability is certainly a factor, history indicates Paterson might not want to base his decision on it.
A review of election results shows that in New York, no sitting Democratic senator has lost an election since at least 1920.
Courtesy of a reader:
Copeland (D, elected 1922) – Houghton (R) 49-48
Wagner (D, elected 1926) – Medalie (R) 56-39
Copeland (D) – Cluett (R) 55-37
Wagner (D) – O'Brian (R) 55-45
Mead (D, elected special election 1938) – Barton (R) 53-47
Wagner (D) – Curran (R) 53-57
Lehman (D, elected special election 1949) – Hanley (R) 50-45
Moynihan (D, elected 1976) – Sullivan (R) 65-34
Moynihan (D) – McMillan (R) 67-32
Moynihan (D) – (R) Castro 55-42
Schumer (D, elected 1998) – (R) Mills 71-25
Clinton (D, elected 2000) – (R) Spencer 67-31