This article is from the archive of our partner National Journal

In the last month, Scott Brown has transformed the New Hampshire Senate race into an unexpected, nail-biting contest. The state's unique sensitivity to nationalized politics, and its proclivity to ride the wave, is at the core of his success.

Initially, Brown's chances of capturing the Senate seat appeared slim to none. The former Massachusetts senator faced charges that he was a carpetbagger and was forced to fight off accusations that his candidacy was blatantly opportunistic. Yet Brown has found his footing in recent weeks by parroting one of the most popular attack themes on the campaign trail this cycle: Sen. Jeanne Shaheen is in lockstep with President Obama, who has a 39 percent approval rating in the state.

"It feels like a significantly different race than it did a month ago," says longtime Republican operative and former New Hampshire Attorney General Tom Rath. "There is no question the president's slide in New Hampshire is dramatic. The Brown campaign has done a very good job making that the central theme of this race."

Rath says he's not confident Brown can win, but if he does, it's because the former senator has run one of the best nationalized campaign of the cycle in a place where voters love to be part of a good swing election.

In the past, New Hampshire's elections have proven to be litmus tests of the national mood. In 2006, when the Iraq War was in full swing and anti-Bush sentiment was growing, New Hampshire for the first time in nearly a century elected two Democrats to fill its congressional delegation. Two years later, Shaheen managed to oust Republican Sen. John Sununu by accusing him of being nothing more than a puppet for an unpopular president.

"I've acknowledged that John Sununu has voted 10 percent of of the time independently. He's voted 90 percent of the time with President Bush," Shaheen said on the debate stage in 2008. "It is those votes for those policies that have gotten us into the economic crisis that we are in."

But in 2010, after the Affordable Care Act was enacted, New Hampshire's partisan pendulum swung back in the Republicans' favor as the tea-party wave swept the nation. New Hampshire elected Republican Sen. Kelly Ayotte and sent two Republicans to the House.

Unlike other close races—like those in Arkansas, Kentucky, or Alaska, all conservative states where Obama's approval numbers have been underwater since he was elected in 2008—strong dissatisfaction with Obama's second term in New Hampshire only emerged mid-2013. The president's popularity in the state has continued to wane as foreign policy and national security emerged over the summer as the dominant force on the campaign trail.

A slew of potential 2016 Republican candidates visiting the state this summer and fall have also echoed the message that Democrats are undermining America's place in the world. And Brown has not wasted the opportunity to join in and exploit the Obama administration's struggles overseas.

In ads, Brown never misses the chance to show Shaheen smiling alongside the president. Whether the focus is the danger of immigrants slipping across the border or the potential for ISIS to attack, Brown has found a resonating message in tying Shaheen to Obama's blunders.

At the last New Hampshire Senate debate, Brown's attacks on Obama's management of the Ebola crisis and ISIS, not statewide issues, became the focus of the debate.

"What's not responsible is for politicians to repeat ISIS talking points like they're planning to plant a flag on the front steps of the White House," Shaheen said as she accused Brown of "fearmongering" to win the race.

"She calls it fearmongering, I call it rational fear," Brown countered.

Brown's nationalized message even appears to be convincing some Democrats in the state. In an endorsement this week, Former Democratic state Senate leader Bob Preston released an open letter denouncing Shaheen. His central argument? Shaheen was simply too friendly with a dysfunctional Obama administration.

"Her blind allegiance to the Obama administration has resulted in the problems our nation faces today," Preston wrote in the letter obtained by The Huffington Post.

Unlike in other competitive midterm states like Kentucky or Georgia, where Democratic candidates Alison Lundergan Grimes and Michelle Nunn are running without a legislative record, Shaheen's positions are clearly articulated in the votes she's taken in the Senate. A fairly consistent Democrat, she does vote often with the president, which isn't unusual in a Senate where parties tend to vote in lockstep.

However, even Republicans admit Shaheen's got something working in her favor. The senator and former governor is a beloved statewide politician. Her favorability is among the highest in the country for lawmakers fighting to win reelection this cycle. If Brown looks like he is running against the president, she has tried to bill her campaign as a race for city council.

Shaheen's tried to make the race a referendum on roots and what she's delivered for the state. On the trail, she touts her ability to secure funding for infrastructure and keep the Portsmouth Naval Shipyard open for workers.

Democrats also brag Shaheen's got the edge when it comes to turning out voters on Election Day.

"The organizing groups have taken the same model they used in the last presidential race and plugged it into this one," says Jim Demers, a Democratic operative who served as a state cochair for Obama's presidential campaign. "What people don't see is all the grassroots organization.... It is far better than what the Republicans have put together."

After all, Brown only became eligible to vote in the state in the last year. To make up for lost time he has tried to overcome his outsider status by driving across New Hampshire in his legendary pickup truck, dropping in on the early-primary state's diners and businesses where voters expect to see politicians shaking hands and working for votes.

If Brown wins, however, it's not likely to be because of his superiority as a candidate or the miles on his truck. A Brown victory would have much more to do with New Hampshire's tendency to get swallowed up by national sentiment on Election Day.

This article is from the archive of our partner National Journal.

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