BOSTON (Reuters) - Voter disenchantment in liberal Massachusetts with President Barack Obama’s policies has turned a Senate election into a nail-biter that could imperil U.S. healthcare reform.

Massachusetts Attorney General Martha Coakley speaks to supporters in Boston, Massachusetts December 8, 2009. REUTERS/Brian Snyder

Democrats envisioned a smooth passing of the baton in the January 19 special election to fill the seat of the late Edward Kennedy, a political giant who died of brain cancer in August after holding the seat for 46 years.

A victory would maintain the Democrats’ 60-seat Senate majority, allowing them to overcome Republican procedural hurdles that could block reform of the $2.5 trillion healthcare sector, Obama’s top legislative priority.

Instead, some polls say the race between State Attorney-General Martha Coakley, 56, and her Republican opponent, State Senator Scott Brown, is too close to call.

“The closeness of the race reflects deep voter dissatisfaction with how the president and the congressional majority are dealing with vital matters,” including healthcare and the war on terror, said Mark Landy, a political science professor at Boston College.

Both sides are pouring millions of dollars into the northeastern state to buy television advertising, much of it negative, and Democrats are bringing out their big guns for Coakley’s final push.

Obama made a personal pitch for the candidate via e-mail and a Web video on Thursday. Former President Bill Clinton, who is popular in the state, will stump for Coakley in Boston on Friday. And the Kennedy family has come out in force this week on her behalf.

Raising the stakes for Democrats, Brown has vowed to vote against the health care bill should he pull off an upset win.

To forestall that possibility, Secretary of State William Galvin, Massachusetts’ top election official, said on Wednesday certifying the election results could take weeks.

Until the winner is certified and seated, interim Sen. Paul Kirk, a Democrat, would remain in the Senate and has said he would vote for the health care bill.

“THE PEOPLE’S SEAT”

Surveys over the past week suggest the election could be anything from a double-digit Coakley cruise to a statistical tie. Republicans last held a U.S. Senate seat in the New England state more than four decades ago.

But Brown, 50, an attorney, former model and Lieutenant Colonel in the Army National Guard, threw down the gauntlet on Monday in a debate with Coakley.

“It’s not the Kennedys’ seat, it’s not the Democrats’ seat, it’s the people’s seat,” Brown said.

2010 was already shaping up as a rough year for Obama and the Democrats. The party in power typically loses seats in an off-year election after a Presidential victory.

But the possibility of losing a seat in the most liberal state in the country -- and Kennedy’s old seat at that -- shows the extent of Obama’s troubles.

As the campaign winds down Democrats have tried to link Brown to the policies of former President George W. Bush, noting he is opposed to financial reform on Wall Street.

DON’T TAKE US FOR GRANTED

Regardless of the national mood, Coakley’s bigger risk is a voter backlash against Massachusetts’ long history of one-party rule and political corruption, said Thomas Whalen, a political historian at Boston University.

The state’s Democratic Party is seen as rife with scandal. Three consecutive former Massachusetts House speakers have been indicted and three state senators have resigned in disgrace in the past two years for various infractions.

“Voters are very angry at the way things have turned out locally; the way the state’s Democrats have abused their power with one scandal after another,” Whalen said. “The message of this election is ‘don’t take us for granted,’ and Martha Coakley is collateral damage.”

In the end, Coakley’s support in western Massachusetts, her backing by many women’s groups, and the Democratic Party’s more effective get-out-the-vote apparatus could pull out a narrow victory that weeks ago seemed all but assured.