Nebraskans head to the polls today to vote in their state's primary, but the Republican Senate race is likely driving the bulk of the turnout.

Both parties will choose their respective nominees to face off in the state's Senate race, which was left open after the Democratic Sen. Ben Nelson decided not to seek re-election. Republicans have long viewed Nebraska as one of their best chances to pick up a seat from the Democrats, even before Nelson announced his plans to retire. Party officials have been unable to harness their attacks on the Democrats, however, because the GOP candidates have been engulfed in a competitive and contentious primary.

There are five candidates on the Democratic primary ballot, but the race is not considered competitive. Bob Kerrey, the former governor and senator for the Cornhusker state, is widely expected to be the nominee.

It's a different story in the Republican primary. There are six candidates on the ballot, but the race is widely considered to be between two people; Jon Bruning, 43, the state's attorney general, who has been and continues to be viewed as the front-runner, and Deb Fischer, 61, a state senator. Don Stenberg, the state treasurer, had previously been viewed as the major challenger to Bruning, but recent polling shows him in third place.

At first glance, the narrative of the primary battle seems familiar. The GOP "establishment" candidate - Bruning - faces a strong challenge from a so-called Tea Party candidate, Fischer. But that's not the case here, for many reasons.

First and foremost, the leading candidates differ little in their positions.

"It's been a difficult race to kind of analyze because the policy positions are really so similar," said John Hibbing, professor of political science at the University of Nebraska-Lincoln. "They're really kind of cut from the same cloth, especially in a state like Nebraska, which leans conservative."

Second, Fischer's only Tea Party support came from Sarah Palin, who endorsed the state senator recently.  The Tea Party label applies best to Stenberg.

He had a great deal of financial assistance from Tea Party-affiliated groups such as FreedomWorks, the Club for Growth and the Senate Conservatives Fund, the PAC affiliated with South Carolina senator and Tea Party leader Jim DeMint. These groups spent relatively large amounts of money supporting Stenberg and attacking Bruning, but Stenberg's campaign didn't seem to take off, for reasons indeterminable to political experts in the state.

"The support for the Tea Party is pretty strong among Republicans here in Nebraska," Hibbing said. "So I think the perception that he was getting supported outside the state by people who were very serious about cutting taxes, I don't think that's hurt him really. He had some money and he doesn't seem to have capitalized on it. "

Fischer, by comparison, had significantly less money than Bruning and Stenberg, and she didn't begin to perform well in polling until recently. In addition to Palin's endorsement, Fischer also received the backing of Nebraska Republican Rep. Jeff Fortenberry. But the reason for her surge likely had more to do with the negative attacks Bruning and Stenberg lodged at one another, rather than these endorsements.

"I don't think it was the endorsements," Hibbings said. "They happened pretty late in the game."

If Fischer wins, it will still be a surprise, and could be categorized as an upset. But that's not because she is considered to be too far to the right, or different from Bruning in a policy sense. It's simply because she was an underdog who did not enjoy the same fundraising advantages or name recognition as Bruning.

Regardless of the outcome, the spirited primary likely won't hurt Republicans' chances in the state heading into the fall.

"I'm sure they wish it hadn't happened," Hibbing said, "but I'm sure it will have a pretty minimal long-term effect. Whoever wins will probably still be favored to win in November."