Amid a struggling economy, a raft of foreign-policy headaches, and the tail end of a heated campaign season, President Barack Obama carved out time in his schedule last month to watch students in the State Dining Room demonstrate a solar-powered model car, a water-purification system, and a soccer-playing robot. The science fair was the fifth White House event he has personally hosted during the past year or so focused on education in the STEM subjects: science, technology, engineering, and mathematics. Given the myriad issues competing for his attention, it's striking how much Mr. Obama talks about the topic, observers say. When President Obama discusses the issue, he emphasizes the need to inspire more young people to engage in the STEM fields. He also highlights the role of STEM education in helping to drive innovation and scientific discovery, and to maintain the nation's economic competitiveness. While most believe the president's interest in the topic is genuine, some say his advocacy carries political benefits as well.