In a speech on the Senate floor Tuesday, Senate Minority Leader Mitch McConnell posed a provocative question in the wake of the Boston bombings: Have Americans become complacent about the risk of terrorism?
"On 9/11, we were forever disabused of the notion that attacks like the one that rocked Boston yesterday only happen on the field of battle, or in distant countries," McConnell, R-Ky., said.
"With the passage of time, however, and the vigilant efforts of our military, intelligence and law enforcement professionals, I think it's safe to say that, for many, the complacency that prevailed prior to September 11 has returned. And so we are newly reminded that serious threats to our way of life remain."
President Obama on Tuesday felt compelled to remind Americans that they should report to law enforcement any package or situation that seems unusual.
"This is a good time for all of us to remember that we all have a part to play in alerting authorities," Obama said at a news briefing. "If you see something suspicious, speak up."
Even the catchphrase "see something, say something" has become "background noise," according to Michael Greenberger, director of the University of Maryland's Center for Health and Homeland Security.
"It's just a sense that since nothing's happened since September 11, the guard has been let down a bit," he said. "The silver lining from this is they're going to be built back again."
Americans still see terrorism as a high-stakes issue, although it has almost disappeared from their list of the nation's top problems. A Gallup poll conducted in early April and released Monday found zero percent of Americans citing terrorism as the country's most important problem.
Terrorism ranked at 1 percent or below in six similar surveys conducted before that Gallup poll, compared with above 20 percent in the year after the 2001 attacks on the World Trade Center and Pentagon.
Part of this stems from the fact that most Americans believe the country is safer since Sept. 11; two-thirds of respondents held that view in a Washington Post-ABC News poll in 2011.
Julian Zelizer, professor of history and public affairs at Princeton University, said the fact that Americans have not recently experienced a heightened state of alert shows "life just normalized after the attacks and following the creation of a rather elaborate counterterrorism program."
"That is the objective of effective policies," Zelizer wrote in an email. "That said, like before 9/11, it is clear that there are many areas of national security that still need work from sporting events to "soft-target" terrorism in places of commerce like malls. This event is likely to prompt renewed attention to what needs to be done to strengthen our security as much as possible, in those areas."