The heightened partisanship cemented in congressional districts has created havens for both Democrats and Republicans, whose job security now often depends more on pleasing primary voters than on the high-altitude questions facing the nation at large. Mark Wilson/Getty Images hide caption

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If the Democrats do win Pennsylvania, it won't be because they had their convention in Philadelphia, which is already a mother lode of Democratic votes. And if the Republicans wind up winning Ohio, it won't be because they won over a lot of precincts in Cleveland, which is a similarly rich trove of Democratic support in elections at all levels. Matt Rourke/AP hide caption

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President George W. Bush addressed a joint session of Congress shortly after the Sept. 11 attacks, vowing to tap "every resource" to fight terrorism. Two days before the speech, he had signed an Authorization for Use of Military Force passed by Congress. WIN MACNAMEE/AFP/Getty Images hide caption

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President Obama delivers remarks during a meeting with people who wrote him letters explaining how they benefited from the Affordable Care Act in the White House on Tuesday. Evan Vucci/AP hide caption

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President Dwight Eisenhower delivers his State of the Union address before a joint session of the 86th Congress in 1959. Behind him are Vice President Richard Nixon (left) and Speaker of the House Sam Rayburn. AP hide caption

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Speaker John Boehner is handed the gavel by House Minority Leader Nancy Pelosi after being re-elected for a third term to lead the 114th Congress. Pablo Martinez Monsivais /AP hide caption

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