A group of liberal bloggers said it is teaming up with organized labor and MoveOn to form a political action committee that will seek to push the Democratic Party farther to the left. Soliciting donations from their readers, the bloggers said they are planning to recruit liberal candidates for challenges against more centrist Democrats currently in Congress. The formation of the group marks another step in the evolution of the blogosphere, which has proved effective at motivating party activists to give money and time to political campaigns, especially in local races. But it also illuminates a deepening wrinkle for President...