Town Moderator Lynn Christensen, who has overseen elections in Merrimack for 27 years, called it "a major fiasco," blaming the bottleneck on a decision to create one-way traffic in the direction of the Merrimack High School polls.
"That road just cannot handle the volume of people coming in at once," she told CNN. "I believe (the plan) came from the police department. They felt that this was a reasonable way to do it and it sounded good. It just didn't work."
Despite those panicky moments, Christensen said nobody who arrived at the polling place was kept from voting, and she did not hear of police turning away voters.
The polls ended up staying open a little more than an hour past their planned 7 p.m. ET closing time.
"I went to the attorney general's office, the secretary of state's office. They consulted and came back and gave me permission," she said.
It remains unknown how many, if any, potential voters were turned back or chose to go home while still on the road in their vehicles.
Still, she predicted a downtick in turnout at the polling location, despite large turnout around the state.
"I don't know that we're going to make that," she said of matching the 1,000-voter turnout during the 2008 primary.
Voters who arrived just before closing time Tuesday night told CNN that they saw numerous people turning around due to traffic on the road to the polling location.
Renee Beijar, a 26-year-old hospital administrator, said she sat for an hour-and-a-half in a half mile of traffic to cast her ballot for Florida Sen. Marco Rubio.
"I needed to get my vote in," she said. "There was a lot of people turning around. I think that's the only reason I moved a lot otherwise because most of the cars turned around."
Twenty eight year-old Gwen Hurd, who works in college admission, sat in traffic for an hour Tuesday morning before turning around so that she could get to work in time.
She returned to the polls Tuesday night when she heard the polling location would stay open later and cast her ballot for former Fortune 500 executive Carly Fiorina.
The New Hampshire secretary of state's office said earlier that police cruisers had marked the end of the line, effectively preventing anyone behind them from reaching the high school, but that talks continued beyond the initial deadline.
"There's some strategies that are being put into place to try and mark the end the line, in traffic, with police cruisers, so that those voters snarled in traffic will be able to get into the polling place," Deputy Secretary of State David Scanlan told CNN.
"There's still some discussions going on about the end of the day," he added. "But I understand that they have placed police cruisers at the end of the line in traffic so that those voters who have been creeping their way to the polling place on the road will have an opportunity to vote."
Anyone who pulled up behind the cruisers was out of luck, he said: "They've missed the closing of the polls."
"They were pretty liberal about where they established the end of the line in traffic," according to Scanlan, who also told CNN that the Bush campaign -- and no others -- had called his office to "just kind of monitor what was going on."
Scanlan said the attorney general's office was "in contact with the election officials in the polling place."