Republican George Allen has conceded the Virginia U.S. race to Tim Kaine.
With 88 percent of the vote in, Kaine led Allen with 50.6 percent of the vote, or by about 37,000 votes.
The victory denies Republicans an open seat they targeted for more than a year in hopes of ending Democratic Senate rule.
For Allen, it was a bitter second loss for the same seat, one that leaves his once-bright political future in doubt.
Allen held the seat from 2001 to 2007, losing re-election to Democrat Jim Webb in a 2006 campaign marred by Allen's use of the slur "macaca" aimed at a Virginia-born Webb campaign aide of Indian descent.
Kaine, a former Democratic National Committee chairman, depicted Allen as a bare-knuckled GOP partisan hostile toward bipartisan compromise.