Former New Hampshire Gov. Jeanne Shaheen’s (D) decision to run for Senate in 2008 not only puts another Republican-held seat in danger but also guarantees that the Granite State will be a major focus of attention well beyond its first-in-the-nation presidential primary in January.

National liberal groups have been running ads attacking first-term Sen. John Sununu (R-N.H.) for months, and Shaheen’s entry into the race means those attacks are almost certain to escalate.

“I don’t think there’s any question that groups like ours are going to pay more attention to New Hampshire,” said Brad Woodhouse, executive director of Americans United for Change, the Washington, D.C.-based organization that has been hammering Sununu on issues ranging from the Iraq War to stem-cell research to children’s health care.

Woodhouse said Sununu’s political vulnerability makes him increasingly subject to pressure from interest groups looking to move him to the center on key Congressional votes between now and Election Day 2008.

“We’re certainly aware of what’s going on in the political world,” Woodhouse said. “Jeanne Shaheen being in the race will make him look over his shoulder even more legislatively.”

Shaheen’s candidacy also means that EMILY’s List, the Democratic fundraising powerhouse that endorsed Shaheen in her previous statewide campaigns, is prepared to be a major player in New Hampshire this cycle. Shaheen will need to jump-start her fundraising, because Sununu had more than $2.1 million banked as of June 30.

Republicans reacted with equanimity to Shaheen’s announcement Friday that she would seek a rematch with Sununu. In a state that moved resoundingly into the Democratic column last year, Sununu already was in for a tough re-election fight regardless of who the Democratic candidate was going to be.

“Certainly this takes the race up a notch for Sununu and for us but I don’t think this means that Sununu is not going to be a Senator next year — I think he will absolutely be re-elected,” said Rebecca Fisher, communications director for the National Republican Senatorial Committee.

Just as the NRSC moved quickly last week to attack former Virginia Gov. Mark Warner’s (D) record after he announced he would seek the open Senate seat in the Old Dominion, Fisher said Republicans are prepared to remind voters why they preferred Sununu to Shaheen by 4 points in their 2002 matchup.

“We’ve seen this race before and the issues that beat her last time are still a problem in New Hampshire, those haven’t gone away,” Fisher said. “Maybe the voter demographic has changed a little bit — we’re certainly well aware of that. But the education system issues she was so dismal on are still there, the tax issues are still there. John Sununu has tried to be an independent voice fixing a lot of those problems that she created and I think the record will reflect that.”

A major difference between 2002 and the present, however, is that President Bush’s popularity was sky-high back then and is at a low ebb now. Bush personally stumped for Sununu in the closing days of the campaign, but must be considered a major liability this time around.

“There’s excitement to get someone in the Senate that cares about New Hampshire and our priorities and being an independent voice and not standing behind Bush,” said Pia Carusone, communications director for the New Hampshire Democratic Party. “The mood has been all along excitement about this race and someone who will be a voice against the war and for stem-cell research and all these things. Folks are fired up about him and the work ahead.”

But while anti-war fervor helped Democrats flip both of the state’s House seats in 2006 and take control of the Legislature for the first time in decades, Shaheen’s own position on the war may be less explicit than many liberals would like it to be.

She came out in favor of the war funding resolution that Congress was debating in the fall of 2002, and said she supported the Bush tax cuts of 2001.

“If you look at her campaign strategy last time, she had a lot of Republicans coming out for her and she stood by a lot of Republicans. She framed herself as very, very moderate and it’ll be interesting to see how she attacks Republicans and tells voters it’s time for change,” Fisher said.

In her announcement statement Friday, Shaheen, who has headed the Institute of Politics at Harvard’s Kennedy School of Government since April 2005, steered clear of specific policy positions or excessive partisanship.

“I’ve stepped down from my position at the Kennedy School of Government because we have major problems facing this country, and there is an urgent need for real change in Washington,” Shaheen said in the statement. “We’ve proven in New Hampshire that we can work together to get things done. I want to take that common-sense approach to Washington and help get this country moving in the right direction.”

Shaheen was scheduled to speak at greater length about her plans during a news conference on Sunday at her home in Madbury, after Roll Call went to press.

Sununu and Shaheen spent about $9.4 million collectively on their 2002 Senate contest, making it the most expensive race in New Hampshire history.

But while Sununu had to get through a tough primary with then-Sen. Bob Smith (R) before being able to square off with Shaheen in the 2002 general election, it is Shaheen who may face primary opposition this time.

Three candidates have been vying for the Democratic Senate nomination for months: former astronaut Jay Buckey, Portsmouth Mayor Steve Marchand, and Katrina Swett, wife of former Rep. Dick Swett (D-N.H.) and daughter of Rep. Tom Lantos (D-Calif.).

Buckey, the least known of the contenders, plans to remain in the race. But Marchand appeared to be heading to the sidelines at press time Friday, leaving Swett — who had banked almost $1.1 million through June 30 and recently sent out a new fundraising appeal — as the big question mark.

But Democratic Senatorial Campaign Committee Chairman Charles Schumer (N.Y.) left little doubt Friday where his rooting interests lie — with the woman who has held a strong lead over Sununu in several recent independent polls.

“Jeanne Shaheen will be a great candidate and a great Senator,” he said in a statement. “We are excited that someone who represents the best of New Hampshire and American values is our candidate for the Senate.”

Daniel Jackson contributed to this report.