The vote was evidence of a broader change in the race, which—when it began—looked in part a test of whether Cotton's approach to foreign policy would alienate voters. A summer of international crises, punctuated by the beheadings of two American journalists, have upended that assumption, so much so that the Arkansas Democrat-Gazette reported that the Pryor campaign has rejected including foreign policy as a topic in an upcoming showdown between Cotton and the senator.
"We had a huge change in public perception," said Ed Bethune, a former Republican congressman from Arkansas who believes Pryor tried to hurt Cotton earlier in the race by highlighting his aggressive foreign policy. "I think their early calculation has misfired."
Cotton, a former infantryman in the Iraq and Afghanistan wars, is one of four Republican candidates with a military background running in a Senate battleground this year, joining Dan Sullivan in Alaska, Scott Brown in New Hampshire, and Joni Ernst in Iowa. Republicans haven't drawn notice to their military-laden class of recruits, and until lately it hadn't mattered much in the campaigns. But the emergence of foreign policy has thrust their background to the forefront and, in some cases, helped bolster their arguments.
"Folks want to look at people making those decisions and know they've walked the walk," said Kevin McLaughlin, a spokesman for the National Republican Senatorial Committee. He joked that the committee wasn't "clairvoyant" when it recruited so many veterans to run this cycle, but that it's provided a late boost nonetheless.
With President Obama's rating on handing foreign policy and national security at all-time lows, Republicans have seen their overall standing improve. But the dynamic in the Senate elections has manifested itself differently, race-by-race.
In Alaska, for instance, Mark Begich was the only vulnerable red-state Democratic senator to vote "no" on the President's proposal, saying he didn't want to use U.S. money to supply rebels who could one day turn against the country. In an isolated state like Alaska, opting against intervention, while also opposing the unpopular Obama, could still count as a political winner.
And in North Carolina, Republicans will have a tough time attacking Sen. Kay Hagan's foreign policy agenda when her GOP challenger, state House Speaker Thom Tillis, declined to say whether he would have supported the measure.
Democrats also point out that despite the public's shift toward intervention, voters don't want another full-fledged war.
"There is broad agreement that [ISIS] must be destroyed and will be destroyed," said Matt Canter, deputy executive director of the Democratic Senatorial Campaign Committee. "The difference is that Republicans want to take the advice of Dick Cheney and launch another ground war in another Middle East country without a plan."