SCOTT SIMON, HOST:
American flags are flying at half-staff today over the White House, and elsewhere in the country. The shootings in Aurora have silenced politics as usual - at least, for the moment. The Romney and Obama campaigns have both pulled their TV ads from the air in Colorado, a state that had three top political advertising markets in the country this week. NPR's Ari Shapiro reports on a somber day on the campaign trail.