In Tuesday's Republican primary, state Sen. Deb Fischer rode a wave of discontent with the GOP establishment to best Nebraska Attorney General Jon Bruning, the preferred candidate of Washington, D.C.-based Republicans, and Treasurer Don Stenberg in a race that drew national attention from outside groups in its final, unpredictable weeks.
The outcome underscored years-old divisions within the GOP, and set the stage for a competitive general election race that could determine the balance of power in the U.S. Senate.
Fischer's victory marked also another win for the party's anti-establishment movement just a week after a tea party-supported Richard Mourdock beat Indiana Sen. Richard Lugar in that state's GOP primary.
Elsewhere Tuesday, presumptive presidential nominee Mitt Romney inched closer to his all-but-certain nomination with wins in two more states.
Romney was expected to pick up most — if not all — of Oregon's 25 delegates. Nebraska Republicans also picked Romney although no delegates would be allotted in a vote that amounts to a beauty contest. The state's 32 delegates to the Republican National Convention later this year will be determined at the state convention on July 14.
Romney began the day 171 delegates short of the 1,144 needed for the nomination and was on pace to get them before the month ended. He spent his day in Iowa, a competitive general election battleground, criticizing President Barack Obama on voters' top concern, the economy.
"This is not solely a Democrat or a Republican problem," Romney said in Des Moines in a clear pitch to independent voters who will decide the election. "The issue isn't who deserves the most blame, it's who is going to do what it takes to put out the fire."
Idaho voters also picked nominees for state and congressional offices.
But the biggest race Tuesday was Nebraska's GOP Senate primary.
Democratic Sen. Ben Nelson, a two-term moderate, is retiring and both parties are eyeing his seat. Democrats want to keep it to maintain their Senate majority, while Republicans see an opportunity in their drive to win back control of the Senate.
Democrats control the Senate 51-47, plus two independents who caucus with the majority. But the outcome in November of several competitive Senate races could result in a power shift.
Kerrey, who served Nebraska as governor and as a U.S. senator before leaving Congress in 2001 to become a university president in New York, reluctantly agreed to run again to help give Democrats a shot at holding a seat they've long controlled.
A decorated veteran and former Navy SEAL, Kerrey faced questions about his residency and Republicans filed a legal challenge. The Nebraska Supreme Court ruled it had no jurisdiction to consider the challenge, clearing the way for Kerrey to run for Senate.
Republicans in Washington turned to Bruning, who has been successful in statewide races and had raised $3.5 million through the end of April.
But in the final stretch of the Senate campaign, he found his nomination hardly assured.
Fischer, a rancher from rural Nebraska, mounted a feisty campaign that attracted attention and endorsements from former Alaska Gov. Sarah Palin, failed presidential contender Herman Cain and other tea party darlings.
She's also backed by an outside group, created by TD Ameritrade founder Joe Ricketts, that ran TV ads on her behalf.
Stenberg, for his part, has argued that he is the only "genuine, life-long conservative" in the race. He won the backing of Sen. Jim DeMint of South Carolina but failed during his fourth run for Senate since 1996.
Associated Press writers Stephen Ohlemacher in Washington, Margery A. Beck in Omaha, Neb., and Grant Schulte in Lincoln, Neb., contributed to this report.