Nelson was a one-time loser (a 1996 loss to Hagel) before he was elected in 2000.
Vermont’s Bernie Sanders had two Senate losses very early in his career (1972 and 1974), when he ran as a third-party candidate and received less than 5 percent of the vote. But he later represented the entire state in an at-large Congressional district for eight terms. Sanders was elected in 2006 (32 years after his previous Senate run) as an Independent, but he was the de facto Democratic nominee as well.
The late Sen. Ted Stevens (R-Alaska) also lost two Senate races before being appointed to his seat and subsequently winning a special election and six full terms.
Of course, losing a Senate race does not guarantee victory, and Stenberg could go the way of Republican Alan Keyes — who has managed to lose two Senate races in Maryland (1988 and 1992) as well as one in Illinois (against Barack Obama in 2004) — and Christine O’Donnell, who has now lost three Senate races in Delaware (2006, 2008 and 2010).
In North Carolina, Erskine Bowles (D) lost races in both 2002 and 2004, and former Charlotte Mayor Harvey Gantt (D) went home empty-handed in 1990 and 1996. In Colorado, Democrat Tom Strickland lost in 1996 and 2002 and Republican Bob Schaffer lost in 2004 and 2008. Former Rep. Ed Bryant (Tenn.) couldn’t get out of Republican primaries in 2002 or 2006.
Correction: May 13, 2011
An earlier version of this story misstated the leadership title of then-Senate Minority Leader Tom Daschle (D-S.D.) when he was defeated in 2004.