By Scott Malone
BOSTON (Reuters) - Republican Scott Brown, a former Massachusetts Senator, plans to launch his campaign to represent New Hampshire in the U.S. Senate on Thursday with an attack on incumbent Democrat Jeanne Shaheen's vote for Obamacare.
Brown, who moved to his native New Hampshire late last year to explore a run for office, has focused much of his energy on attacking the Affordable Care Act, an issue that Republicans are making a centerpiece of 2014 campaigns.
"I worked with Senator Shaheen in the U.S. Senate for three years. She is a nice person, but wrong on the issues facing the people of New Hampshire," Brown will tell supporters in Portsmouth, New Hampshire, according to excerpts of his planned remarks provided by his spokeswoman.
"She made that clear when she cast the deciding vote that forced Obamacare on this state and our country," he will say.
The Affordable Care Act passed the U.S. Senate in 2010 by a margin of 60-39, with all Democrats, including Shaheen, voting in favor of the measure, which was President Barack Obama's top domestic priority.
The rollout of the new system has been plagued with technical glitches. A poll of New Hampshire voters released in February found that 53 percent of adults in the state opposed the law, while 34 percent favored it, a finding that made Obamacare less popular in the New England state than nationally.
Despite the early challenges that slowed online registrations, the White House released figures last week showing that 7.1 million people had enrolled through the exchanges set up by the act, exceeding most expectations.
Brown has quickly won support from national Republican groups who see the seat as one of their opportunities to reclaim a majority in the Senate, which Democrats currently control by 55 seats to the Republican's 43.
Polls show Brown trailing Shaheen in support among likely voters, though his candidacy has quickly become a top concern of state Democrats who began raising his specter in fundraising e-mails after his move to the state.
Observers say he is likely to draw significant amounts of money for television ads from outside the state.
"Both parties are clearly going to be putting money into this because there are about 10 seats that could flip and this is obviously one that Democrats want to hold," said Shep Melnick, a professor of political science at Boston College who has been active in New Hampshire Democratic politics.
"The money thing will probably be a wash because if it looks competitive, both sides will pump money in," he added.
(Reporting by Scott Malone; Editing by Dan Grebler)