Republican Senate candidate Scott Brown

Republican Senate candidate Scott Brown defeated his Democratic rival on Tuesday in Massachusetts special Senate election, according to preliminary calculations of the votes.

With 93 percent of the total votes calculated, Brown, the state senator, seized 52 percent, leading Democrat Martha Coakley, the state attorney general, 5 percentage points.

Coakley has called Brown to concede her defeat.

With Tuesday's victory, Brown will fill the seat of Democratic Senator Edward M. Kennedy, who died in August after nearly 47 years in office.

This dealt a big blow to President Barack Obama and Congressional Democrats by robbing Democrats of their Senate supermajority and jeopardizing their efforts to reform the healthcare system.

Brown has vowed to cast the 41st vote that Republicans need to filibuster -- a procedure used to stall and defeat legislation -- the final passage of the House-Senate compromise on healthcare bill.

Still, Obama sent his congratulations to Brown.

"The president congratulated Senator Brown on his victory and a well-run campaign. 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," White House spokesman Robert Gibbs said in a statement.