In a political shocker, a Republican won the US Senate seat long held by liberal champion Edward M. Kennedy, dealing a huge blow to US President Barack Obama and his health care overhaul plan just as he concludes his first year in office. Republican Scott Brown rode a wave of voter anger to beat Democrat Martha Coakley in Tuesday's special Senate election in Massachusetts. The loss was a stunning embarrassment for the White House. It also signaled big political problems for the president's party this fall when House, Senate and gubernatorial candidates are on the ballot nationwide. With Brown's victory in Massachusetts, Senate Democrats lost the 60-vote supermajority needed to achieve Obama's top goals. That could doom the health care bill and make it more difficult to pass legislation on climate change and other top White House priorities. The vote bodes poorly for Democrats ahead of November's congressional elections. If they cannot win in a Democratic stronghold, defending Kennedy's seat against a relatively unknown state senator like Brown, they could be vulnerable almost anywhere. Democratic lawmakers could read the results as a vote against Obama's broader agenda, weakening their support for the president. And the results could scare some Democrats from seeking office. Just weeks ago, Coakley, the state attorney general, had a double-digit lead in polls and seemed destined to win. Her defeat was an embarrassment for the White House after Obama rushed to Boston on Sunday to try to save her campaign. Obama carried Massachusetts by 26 percentage points over Republican John McCain in the 2008 presidential election. Brown led by 52 percent to 47 percent with 99 percent of precincts counted. The third candidate in the race, independent Joseph L. Kennedy, who is no relation to Edward Kennedy, had less than 1 percent. Turnout was exceptional for a special election in January. The election highlighted the dramatic reversal for Democrats one year after the euphoria of Obama's Jan. 20, 2009, inauguration as the first black US president. The anti-incumbent mood that lifted the party in the 2008 election is now pushing against Democrats, with voters frustrated by high unemployment, bank and auto industry bailouts, exploding federal budget deficits and partisan wrangling over health care. Brown's victory was the third major loss for Democrats in statewide elections since Obama became president. Republicans won governors' seats in Virginia and New Jersey in November. “I have no interest in sugarcoating what happened in Massachusetts," said Sen. Robert Menendez, the head of the Senate Democrats' campaign committee. “There is a lot of anxiety in the country right now. Americans are understandably impatient." Brown seized on voter discontent to overtake Coakley in the campaign's final stretch. His candidacy energized Republicans while attracting disappointed Democrats and independents. Adding to the Democrats' dismay is that Brown won Kennedy's seat by promising to oppose the health care overhaul - an issue closely identified with the senator. Brown's victory was so sweeping, he even won in the Cape Cod community where Kennedy died of brain cancer last August. “While the honor is mine, this Senate seat belongs to no one person, no one political party,” Brown told his supporters Tuesday night. “This is the people's seat," he added to chants of “People's seat!” Brown became the first Republican elected to the US Senate from reliably Democratic Massachusetts since 1972. He will become the 41st Republican in the 100-member Senate, which could allow Republicans to block the health care bill. Democrats needed Coakley to win for a 60th vote to thwart Republican legislative maneuvers to prevent a final vote on a bill. Obama has made health care his signature issue, looking to revamp an expensive, inefficient system that leaves nearly 50 million people uninsured. Republicans have almost unanimously opposed his plans, saying it would lead to higher taxes and government meddling in health care decisions. Obama has tried to avoid repeating the experience of Bill Clinton, who saw Democrats lose control of Congress in 1994 after he unsuccessfully pushed for a health care overhaul early in his presidency. Democrats have pushed health care close to enactment, passing separate bills in both chambers of Congress. In the Senate, Obama needed every vote in the Democrats' 60-member caucus to overcome Republican procedural hurdles. But another Senate vote will likely be necessary and, once Brown takes office, Democrats will no longer have those 60 votes. They could try to win the support of a moderate Senate Republican, though they have had little success with that so far. They could also attempt some politically risky maneuvers, but it's unclear that they can get enough support from their own fractious lawmakers, who are divided on abortion provisions and other issues. Brown will finish Kennedy's unexpired term, facing re-election in 2012. Senate Majority Leader Harry Reid pledged to seat Brown immediately, a hasty retreat from pre-election Democratic threats to delay his inauguration until after the health bill passed. Coakley called Brown conceding the race, and Obama talked to both Brown and Coakley, congratulating them on the race. She said the president told her: “We can't win them all.” But even before the first results were announced, administration officials were privately accusing Coakley of a poorly run campaign and playing down the notion that Obama or a toxic political landscape had much to do with the outcome. Coakley's supporters, in turn, blamed that very environment, saying her lead dropped significantly after the Senate passed health care reform shortly before Christmas and after the Christmas Day attempted airliner bombing that Obama himself said showed a failure of his administration.