His spokeswoman, Lis Smith, said it was "a day to reflect on Senator Mikulski's service to the people of Maryland, not engage in political speculation."
Martin O'Malley now has 2016 option: A run for president, or Senate →
"While they outraised us, and traditionally outraise us by a sizable amount, they also outspent the DGA by a sizable amount," DGA spokeswoman Lis Smith said. "A strategic deployment of resources beats out a big, flashy deployment of resources."
McDonnell nets record haul for GOP governors →