AP
Brown drew national headlines when he won the seat previously held by the late Sen. Ted Kennedy (D-Massachusetts) in a huge 2010 upset, only to lose his re-election bid against now Sen. Elizabeth Warren (D) in 2012.
Brown proceeded to switch states and challenge Sen. Jeanne Shaheen (D-N.H.) this year.
Polls showed his race to be a reach for Republicans, but had they won it, his victory could have been a potential sign of wide GOP pickups across the country.