WASHINGTON >> Bob Kerrey won the Democratic nomination for Nebraska’s open U.S. Senate seat Tuesday while Republicans decided a tight three-way race that reflected the divisions within the GOP.

Kerrey, a former senator seeking another turn on Capitol Hill in one of the year’s most contested Senate races, easily captured the Democrats’ nomination.

Officials continued to count votes in the primary that illustrates the split between the establishment Republicans who favored State Attorney General Jon Bruning and tea partyers who helped state Sen. Deb Fischer make a late play for the nomination. State Treasurer Don Stenberg also was on the ballot for his fourth attempt to become a U.S. senator.

Early returns showed a close race between Bruning and Fischer, with Bruning enjoying a narrow lead.

Elsewhere, Oregon was deciding whether to give its 25 presidential delegates to Mitt Romney, the all-but-certain GOP nominee. Nebraska Republicans 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 was 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 were picking 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 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 has found that his nomination is hardly assured.

Fischer, a rancher in rural Nebraska, mounted a feisty campaign that in the past few weeks 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’s running TV ads on her behalf.

"Nebraska seems to like underdogs, and I hope that continues through Tuesday," Fischer said.

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 has failed each of the three times he has run for Senate since 1996.