Effort for Liberal Balance to G.O.P. Groups BeginsBy MICHAEL LUO Published: November 23, 2010 In what may prove a significant development for the 2012 elections, David Brock, a prominent Democratic political operative, says he has amassed $4 million in pledges over the last few weeks and is moving quickly to hire a staff to set up what he hopes will become a permanent liberal counterweight over the airwaves to the Republican-leaning outside groups that spent so heavily on this year’s midterm elections. Kathleen Kennedy Townsend, a former Maryland lieutenant governor and the eldest of Robert F. Kennedy’s 11 children, has...