Less than two years ago, Amy Kremer and Jenny Beth Martin were 30-something suburbanites in metro Atlanta, frustrated by recession, dismayed by the election of Barack Obama and waiting for the next chapter of their lives. Ms. Kremer, a former Delta Air Lines flight attendant, had quit her career to raise her daughter. The child had grown up and just moved out, and now Ms. Kremer was filling her time with two blogs—one on gardening, one on politics. "I had this empty space in my life," Ms. Kremer recalls. Ms. Martin, a software manager by training and part-time blogger, was...