In his speech to the nation last Wednesday, announcing troop withdrawals from Afghanistan, President Obama said we needed to refocus on nation-building here at home. This idea echoes the massive ambitions of President Lyndon Johnson’s Great Society in the 1960s. Johnson’s situation seems to somewhat mirror President Obama’s: Johnson brought us the Civil Rights Act, Medicare and Medicaid, but his broader ambitions were eventually sidelined by the fiscal necessity of Vietnam. To examine this further, we speak with historian Robert Caro, the author of the multi-volume, Pulitzer Prize-winning biography, “The Years of Lyndon Johnson.”