Biden's old Senate seat eyed by son Beau, top Republican challenger
"Dramatically alters the dynamic of the race," said the Rothenberg Political Report, which handicaps House and Senate races and has now moved the race from "leaning Democrat" to "leaning takeover."
His likely opponent is Beau Biden, the vice president's son and a former state attorney general who recently returned from a year-long deployment in Iraq and is now weighing the race.
Castle's entry was seen as a big boost for Republicans, perhaps their best shot at taking a Democratic seat in 2010. The state is traditionally blue, but the 70-year-old moderate Republican is historically popular.
During last summer's town halls of rage, Castle defended President Obama when a voter asked him about the president's birth certificate.
“If you’re referring to the president, then he is a citizen of the United States," Castle replied. When the crowd then erupted in boos and shouts for him to "Prove it!" Castle sighed and said, "You can boo, but he is a citizen of the United States.”
-- Johanna Neuman
Photo: Mike Castle at a contentious hearing in March at which AIG executives tried to defend giving out bonuses amid a government bailout. Credit: Chip Somodevilla / Getty Images