Sen. Tom Carper, D-Del., announced Monday that he will not seek re-election after 20 years in the Senate, instead focusing on clean energy, tackling global warming and spurring economic growth. He has served in public office for nearly 50 years, beginning in 1970, and is confident his former intern, Lisa Blunt Rochester, will make an excellent successor. Carper is proud of the work he has done in the Senate and is looking forward to the next 20 months.