Elections change the political conversation in slow motion—as candidates decide to run, as they appeal for votes, as they translate words into action after taking office.
But horrifying events in the world—like this week's attacks in Paris—change it instantly.
Congressional Republicans had established February as the month that funding for the Department of Homeland Security would run out as they seek to block President Barack Obama's executive action on immigration. Their chances of succeeding were always dim; now they are dimmer.
"I've never been for shutting down Homeland Security," Republican Sen. Lindsey Graham of South Carolina said in one television interview. As a top Senate Democratic aide put it, "It makes it harder to talk about defunding with a straight face."
The brazen killings at the French magazine Charlie Hebdo put pressure on Obama in different ways. Just as improving economic numbers were beginning to brighten the public mood, fear of terrorism could dampen it again,
Obama has planned to focus this year on steps to improve America's economic future while implementing the wind-down of the war in Afghanistan. Anxieties over his security strategy—which will rise now as they did after last year's savagery by the Islamic State—do not help.
That doesn't mean he will change his strategy. Richard Haass, a former national security side to President George W. Bush who now heads the Council on Foreign Relations, said there's no need to.
"We need to be vigilant, continue working with Muslim community leaders, reverse momentum in Iraq and Syria, and keep getting the truth out about how bad it is under ISIS rule," Haass said.
But Peter Feaver, a Duke University professor who also advise Bush, suggested the attacks point toward a fundamental softness in Obama's approach. His argument will echo throughout Washington security debates.
"The horrible Paris attacks reflect the profound asymmetry in this conflict," Feaver said. "The West views this primarily as a debate fought with the weapons of rhetoric.
"The terrorists view this as a war fought with bullets and bombs. It is hard to debate someone who thinks they're at war with you."
James Steinberg, a former Obama State Department official now at Syracuse University, pointed to a different shift in domestic politics. The ongoing debate over the proper balance between surveillance and civil liberties, which escalated after disclosure of National Security Agency data collection in 2013, suddenly has a new tenor.
"It will slow momentum for curbs on the NSA and the FBI," Steinberg said.