Once largely dismissed by critics as an unlikely second act in a state he moved to only last year, Brown’s Senate bid is increasingly seen as a plausible path back to the US Capitol.

Analysts and recent polls have found Brown closing in on US Senator Jeanne Shaheen, the Democratic incumbent he is vying to unseat, in a race that has become increasingly nasty and expensive.

SALEM, N.H. — Voters have soured on President Obama. National and statewide trends favor Republicans. And here in his new home state, Scott Brown’s truck is gaining speed.

Observers see a race that may be largely determined not by Brown, a top-notch retail campaigner, or by Shaheen, a popular, longtime elected official, but by the national mood.


“In wave elections, as people find out, you can have been a good candidate and done a good job for your constituents and still find yourself swept out,” said Steve Duprey, New Hampshire’s Republican national committeman. “If there’s a national tide, it will roll here too.”

On the stump and in TV ads, Brown constantly ties Shaheen to Obama, who has a job approval rating of just 38 percent among likely New Hampshire voters, according to one poll released this week. The former Massachusetts senator rarely misses an opportunity to express his dismay that Shaheen votes in lockstep with the president or to nationalize the race, speaking about issues such as immigration and the threat from the burgeoning militant group in Iraq and Syria.

Shaheen, a onetime governor, repeatedly underscores her local achievements for the state — from working to protect a shipyard from closure and to helping veterans get easier access to health care. She attacks Brown as more keen on boosting his own career than aiding New Hampshire.

Analysts say Shaheen is running a campaign that fits the state and the darkening climate for her party. Still, the New Hampshire US Senate race “is getting more competitive,” said Jennifer Duffy, a specialist in US Senate races with the nonpartisan Cook Political Report.


She said the tightening in the contest is the result of several factors, including that the Granite State is “unusually susceptible” the national political climate.

Democrats across the state acknowledge Obama is now quite unpopular in a state he won twice, and that the Senate race is genuinely competitive. But they insist that no matter how friendly the terrain has become for the GOP, Brown’s trusty GMC truck doesn’t have the horsepower to overcome a local landscape cultivated for years by a longtime elected official, one who is still seen favorably by voters.

“In the end,” said Terry Shumaker, an active Granite State Democrat for decades and a former US ambassador, ”I don’t think that the president’s approval rating — and it may be much higher on Election Day — will trump Jeanne Shaheen’s reservoir of goodwill, all the things she did as governor, all her accomplishments as senator.”

He argued that voters in New Hampshire are sophisticated and know the difference between their senior senator and the president.

Duprey, the Republican committeeman, said that Shaheen knows “every nook and cranny of New Hampshire,” is very likable, and has one of the best constituent services operations.

But he said, because Shaheen votes so frequently with Obama, she has become inextricably linked to the president as his star falls and as the country’s foreign policy picture grows more grim.


The increasingly competitive contest is part of a national landscape in which Republicans are trying to win a net of six seats necessary to take control of the US Senate.

National Democrats remain bullish on the New Hampshire race, saying Shaheen remains somewhat insulated from the prevailing winds. They point to a series of public polls that indicate likely voters see her more favorably than unfavorably, while more voters see Brown unfavorably than favorably.

But Brown aides say that their candidate’s emphasis on Shaheen voting so closely with Obama is having an impact, and their polling data show voters are starting to view the incumbent as part of the problem in Washington.

At a campaign event Wednesday, Brown said he is working hard to talk about the issues, from immigration to the Islamic State in Iraq and Syria to the Affordable Care Act.

“She can’t talk about those things because she is voting with the president 99 percent of the time,” he said, bemoaning the “constant barrage of negativity.”

Shaheen and her allies have been on the attack against Brown, saying in various ways that he’s looking out for himself, not everyday folks.

In a statement, Shaheen campaign manager Mike Vlacich said, “Since moving to New Hampshire just under a year ago, Scott Brown’s biggest accomplishments has been for himself.” He pointed to Brown’s position on the board of a company that Vlacich said has outsourced jobs overseas.


He echoed the tagline of a recent ad that savaged Brown: “Scott Brown. Not for New Hampshire. Never was. Never will be.”

Brown allies and aides brush off the attacks from Shaheen and her Democratic allies — part of millions of dollars in spending from both sides in the contest — as not particularly effective.

“There are so many attack ads in the water right now, I just don’t think they’re cutting through,” said campaign manager Colin Reed.

While ads on the airwaves can shift a race, the national climate is likely to have the biggest impact, analysts said. In recent elections where there was a national wave of support for one party, many races in New Hampshire went with it.

For example, in 2006, as voters weary of President George W. Bush swept Democrats to the majority in the US House, New Hampshire voted Democrats into both of the state’s congressional seats. In the GOP banner year of 2010, Republicans took back both congressional seats and won the open US Senate seat.

Dante Scala, a political science professor at the University of New Hampshire, said Shaheen is “walking a tightrope right now, and that has a lot to do with the national environment.”

He noted polls have found she is more popular than the president, meaning there is a category of voters who see her, but not the president, favorably.

More from today's paper Between now and Nov. 4, he said, “Scott Brown’s job is convert as many of those voters as possible.”

Noah Bierman of the Globe staff contributed to this report. Joshua Miller can be reached at joshua.miller@globe.com. Follow him on Twitter @jm_bos.