Florida Sen. Marco Rubio, shown here at an event in Washington last month, spoke with NPR's Morning Edition about the country's economic challenges. Molly Riley/AP hide caption

itoggle caption Molly Riley/AP

Harvard Square, a large triangular area located in the heart of Cambridge and adjacent to Harvard University and near MIT University — two of the world's top-ranked institutions of higher learning. Darren McCollester/Getty Images hide caption

itoggle caption Darren McCollester/Getty Images

President Obama takes the stage at the University at Buffalo on Thursday. Jacquelyn Martin/AP hide caption

itoggle caption Jacquelyn Martin/AP