A Republican opponent of President Barack Obama's healthcare reform plans has won the US Senate seat formerly held by the late Edward Kennedy in Massachusetts.
Scott Brown won the election in Massachusetts to be the deciding vote against US President Barack Obama's sweeping healthcare overhaul.
Mr Brown's win robbed Democrats of the crucial 60th Senate vote they need.
What once seemed an easy Democratic victory turned into a desperate scramble in the last few weeks as Mr Brown surged ahead of Democratic state Attorney General Martha Coakley on voter fears over the economy, the healthcare bill and Mr Obama's agenda.
Mr Brown, a Massachusetts state senator, said he would be the pivotal 41st Republican vote against the healthcare overhaul in the 100-member Senate.
'People don't want this trillion-dollar healthcare plan that is being forced on the American people,' Mr Brown told supporters at a Boston hotel.
He said voters rejected the closed-door deals that were driving the healthcare debate, and he took satisfaction in proving the experts and Democrats wrong.
'They thought that they owned this seat. They thought that they couldn't lose,' Mr Brown said. 'You all set them straight.'
Mr Brown's upset with 52% of the vote in heavily Democratic Massachusetts raised the spectre of large losses for Democrats across the US in November's elections.
'Anyone who has been out on the campaign trail has seen the anger,' Ms Coakley, who was criticised for running a weak campaign, told a room of dispirited supporters at a Boston hotel. 'I am heartbroken at the result.'
Mr Obama made a last-minute appeal in Massachusetts on Sunday to try to ignite enthusiasm for Ms Coakley's campaign to replace the late Senator Edward Kennedy, a Democratic icon and long-time champion of healthcare reform.
In Washington, Mr Obama spokesman Robert Gibbs said the president called Mr Brown after the result.
'The president told Senator Brown that he looks forward to working with him on the urgent economic challenges facing Massachusetts families and struggling families across our nation,' Mr Gibbs said in a statement.
US Senate Democratic leader Harry Reid said he would welcome Mr Brown to the Senate as soon as he received the paperwork from Massachusetts officials.
'I believe it would only be fair and prudent that we suspend further votes on healthcare legislation until Senator-elect Brown is seated,' Democratic Senator Jim Webb said.
Massachusetts last elected a Republican to the Senate in 1972.
