Gov. Jack Markell (D) is term limited and will exit office in 2017.
Beau Biden, 45, is a popular figure who was easily reelected in 2010. Viewed for years as a rising star, he flirted with a 2010 Senate bid before declining to run. The Democrat underwent treatment at a Texas cancer center last year. A doctor on his medical staff said in February that he has a "clean bill of health."