The Harvard Law professor and consumer advocate had narrowly been favored in recent days, as polls showed her with a slight lead over the incumbent senator.
Warren was the intellectual godmother of the Consumer Financial Protection Bureau and was its first head. She was denied a permanent appointment due to objections from congressional Republicans and from within the Treasury Department.
From the beginning, the Massachusetts Senate race attracted national attention. Brown, who opposed Obamacare, won election to the Senate in a 2010 special election at the height of the health care reform debate following the death of Sen. Ted Kennedy (D-Mass.) Warren's impassioned advocacy for economic fairness caused liberals to rally around their candidacy. Democrats were eager to reclaim the seat that Kennedy held for over four decades.
As a result, Warren became one of the top Senate fund-raisers of all time, surpassing Hillary Clinton's 2000 Senate run. Brown was also successful in fundraising, having a significant war chest from his 2010 run.
The race was neck-and-neck for most of the race, but Warren pulled away narrowly after her speech at the Democratic National Convention in Charlotte, N.C. In September.
Warren stressed that the race was about control of the Senate, and tied Brown to the national GOP. Brown distanced himself from other Senate candidates like Todd Akin of Missouri and Richard Mourdock of Indiana. In the end, Warren had an easier lift as a Democrat in a deep blue state, and Brown's moderate image only carried him so far.
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