May 23 (Bloomberg) -- Hillary Clinton, Barack Obama and the rest of the Democratic presidential candidates may be about to welcome a host of party-crashers: New Hampshire's independents.

Eight years ago, the independents -- who are a plurality of the voters in the first-in-the-nation presidential primary -- chose in overwhelming numbers to vote in the Republican contest, fueling Arizona Senator John McCain's victory.

Next year, according to the University of New Hampshire Survey Center, more than two-thirds of independents plan to vote in the Democratic primary, driven by a desire for change and dissatisfaction with the Iraq war and President George W. Bush.

``They'll crash the party on the Democratic side and leave the Republicans pretty much alone,'' said Dante Scala, an assistant professor of politics at St. Anselm College in Manchester.

That would shape both parties' races, Scala said: To win, Democratic candidates will need to court the independents, while Republicans may focus more on party stalwarts.

Andy Smith, the poll director at the University of New Hampshire in Durham, said the movement of independents to the Democrats might help Obama, the Illinois senator, more than his New York colleague Clinton, who polls show is stronger with the party's base.

`Solid Republican'

Meanwhile, ``for the Republicans, it means your electorate is going to be a solid Republican electorate,'' Smith said. That may benefit candidates such as former Massachusetts Governor Mitt Romney, 60, who is building his appeal around his party's social- and religious-base voters, rather than former New York Mayor Rudy Giuliani, 62, for whom independents are a vital constituency.

The 44 percent of the state's electorate who are registered as undeclared have played this role before, helping give upset victories to Democrat Paul Tsongas in 1992 and Republican Patrick Buchanan in 1996, as well as McCain in 2000.

In last year's mid-term elections, independents helped Democrats oust two incumbent Republican congressmen and, for the first time since 1874, take control of both the governorship and the state legislature.

Changing the Equation

In 2008, the battle for independents is leading Democrats to take up issues outside the party's traditional portfolio, said Larry Rasky, a senior adviser to Delaware Senator Joe Biden. ``The political equation for how you address the issues changes,'' he said. ``It makes it more like a general election.''

Mary Lou Heran, 60, an educational-publications editor from Hampton, may be typical of Granite State independents. Heran previously cast ballots twice for Bush, a Republican, and twice for Bill Clinton, a Democrat. She said she plans to vote for a Democrat in 2008; her reasons -- Iraq and what she sees as excessive partisanship in politics -- echo the major themes of Obama's campaign.

With just two years of experience in Washington, Obama, 45, is casting himself as an outsider capable of bridging partisan divides, a traditional selling point for independents. ``Compared to Hillary Clinton, he's not seen as involved in politics for as long a period,'' Smith said.

Obama is also emphasizing his consistent opposition to the war, drawing another contrast with Clinton, 59, who voted for the 2002 resolution giving Bush authority to invade Iraq.

Opposed From the Outset

In a May 18 speech in Rye, Obama reminded his audience that he opposed the war from its outset and said he understands why many Americans are ``cynical'' about politics, which he said often looked more like ``a business instead of a mission.''

Clinton, who leads in the polls, is trying to fight the impression that she is a Washington insider anointed by party regulars. ``The label of `establishment candidate' is put there by others,'' said Nick Clemons, Clinton's New Hampshire director.

Seeking to appeal to independents, she emphasizes taxes and excessive government spending. In Manchester last month, she announced a 10-point plan to fight waste and corruption, a blueprint that would trim government contractors and curb no-bid contracts.

Bloated government is a favorite issue for many New Hampshire independents such as Ken Braiterman, 58, a mental- health advocate from Henniker who said he mostly supported Republicans in the 1980s.

Frugal and Competent

Independents ``want government to be frugal, competent and out of your individual life,'' he said. ``The current administration in Washington is none of those.'' Still, Braiterman said, he currently favors Obama over Clinton.

With most independents focused on the Democratic primary, Republicans face a different challenge -- rallying their own party's voters.

Fifty-one percent of the voters in New Hampshire's Republican primary call themselves conservative, according to Smith. The independents' drift to Democrats ``is good for conservatives'' like Romney and, if he enters the race, former Tennessee Senator Fred Thompson, said Fran Wendelboe, a self- described conservative Republican who serves in the state legislature.

At the same time, Wayne Semprini, Giuliani's New Hampshire chairman, said he isn't giving up on independents. The Giuliani strategy is to encourage independents to vote Republican while appealing to conservatives on economic issues, including his record in New York City. ``They can call him moderate, they can call him anything,'' Semprini said. ``His results are conservative.''

To contact the reporter on this story: Heidi Przybyla in Boston at hprzybyla@bloomberg.net

Last Updated: May 23, 2007 00:13 EDT