Just saw Chuck Todd discussing it with Jose Diaz Balart on MSNBC. One of the things mentioned was that he felt like he'd be a drain on resources for other Democrats running for the Senate. Stepping down in a year with a presidential election boosts the chances of the Dems retaining the seat.
Republican Dan Coates of Indiana also announced he was leaving the Senate in 2016 this week.
Republican Dan Coates of Indiana also announced he was leaving the Senate in 2016 this week.