Steve Hildebrand was getting an earful. Barack Obama’s soft-spoken deputy campaign manager had just finished a panel discussion at the Netroots Nation convention in Austin, Texas, on July 19, during which he had called on liberal bloggers to help meet the demands of the 24-hour news cycle by beating back criticisms of the candidate. The more people there were participating in the campaign, he argued, the greater the likelihood of Mr. Obama’s election and an enduring Democratic majority.