Massachusetts voters headed to the polls today in an election for a new US senator that could derail Democrats' dominance in Washington.
The special election to fill the seat of the late Democratic veteran Edward Kennedy could see Republican Scott Brown score an upset against Democrat Martha Coakley in what was believed to be one of her party's safest seats.
Latest polls suggest he could defeat state Attorney General Ms Coakley taking away the Democrats' supermajority in congress - reshaping President Barack Obama's agenda after just one year in office.
Mr Kennedy, who held the seat for almost 47 years, died in August.
Massachusetts last elected a Republican to the Senate in 1972.
The Republican candidate has attracted strong support from independent voters, including many who backed Mr Obama in 2008, while Ms Coakley has been criticised for a lacklustre campaign.
The economy and doubts about the healthcare overhaul are thought to have moved voters to reconsider political loyalties.
Their possible change of heart could not have come at a more crucial juncture for Mr Obama.
Democrats now control 60 votes in the Senate to 40 for the Republicans.
The loss of one seat could hamper the Democrats' ability to cut off debate and proceed to a vote on the biggest healthcare reform in the US in more than four decades.
Voter turnout is frequently low in off-season elections, and can be even lower due to bad weather. A messy snowstorm hampered travel yesterday and snow showers might fall today.
Polls were to open 7am (12pm Irish time) until 8pm (1am Irish time).
Given the likely closeness of voting, it could take officials a few hours to declare the winner.
