Delaware ? Vice President Joe Biden’s eldest son, Delaware Attorney General Beau Biden, dealt another body blow to the flailing Democratic Party on Monday, announcing that he will not run for the Senate seat long held by his father.

The younger Biden said he needs to remain focused as attorney general on a high-profile criminal scandal involving a pediatrician accused of sexually assaulting several patients. Prosecutors believe Dr. Earl Bradley, who was arrested in December, may have molested more than 100 children over the past decade.

Some political observers believe there was more to Biden’s decision than staying true to a 2006 campaign promise to crack down on child predators.

Biden’s decision was a surprise, given that his father’s longtime confidant and former Senate chief of staff, Ted Kaufman, was appointed to the seat essentially to keep it warm for the son until this year’s election.

But longtime Republican Rep. Mike Castle, a two-term governor and one of the most successful politicians in Delaware history, entered the Senate race in October, dramatically increasing the likelihood of a fierce contest.