Conservative money has poured into Nebraska's Republican Senate primary race.

Big GOP names like Texas Sen. Ted Cruz and Senate Minority Leader Mitch McConnell are on opposite sides.

And the attack ads have been brutal — including one that took a page directly from the Swift-boating of John Kerry's military record during his 2004 presidential run.

But that doesn't mean the contest to succeed retiring Republican Sen. Mike Johanns is another clear-cut primary battle between the GOP's Tea Party wing and the establishment.

After all, Ben Sasse, the so-called anti-establishment candidate, worked in the Bush White House and spent the better part of last decade in federal jobs in Washington. And the candidate favored by GOP leaders in Washington, Shane Osborn, has support from prominent local anti-tax and Tea Party organizations.

The distinctions are muddled enough that FreedomWorks, a national Tea Party-affiliated group, first backed Osborn before switching gears and throwing its support to Sasse.

"We are on track for some incredible spin on Wednesday morning — some anti-establishment groups are building this up to be a monumental fight," says Nathan Gonzales, who analyzes Senate races for the nonpartisan Rothenberg Political Report. "I just don't think the Nebraska primary fits neatly into the establishment-vs.-anti-establishment battle within the Republican Party."

Sasse, a former congressional staffer and Department of Health and Human Services official, has served as president since late 2010 of Nebraska's Midland College. Osborn, a retired, decorated Navy pilot, is a former one-term state treasurer. Another candidate, multimillionaire Omaha banker Sid Dinsdale, has pumped $1 million of his own money into the race.

The U.S. Chamber of Commerce and the National Republican Senatorial Committee have notably stayed out of the race, leaving the playing field largely to groups like the limited-government Club for Growth and the conservative 60 Plus Association, both backing Sasse.

Osborn, meanwhile, has gotten money from McConnell's leadership PAC. (Sasse angered the Senate minority leader last year by calling for better Republican leadership in Washington, and for accepting an endorsement from the Tea Party-fueled Senate Conservatives Fund, one of the minority leader's harshest in-party critics.)

There's little ideological difference among the three competitive candidates, and no one can lay exclusive claim to Tea Party support. National organizations have gotten behind Sasse — as have noted conservatives such as Sarah Palin — but Nebraska Tea Party activists have pushed back. Last month more than 50 of them signed a statement asserting that Sasse is not their choice.

"Recently," they wrote, "a barrage of radio, TV and direct mail ads from national Washington D.C.-based PAC organizations have swept Nebraska like a plague of locusts."

"These groups claim to know what Nebraska Tea Party, conservative and libertarian movement folks want in their next U.S. senator," they said.

Both Sasse and Osborn have accused the other of not being enough of a Nebraskan. Osborn has sought to paint Sasse as a Washington insider; the Sasse camp counters that Osborn, while in the military, registered to vote in Florida while stationed there and once suggested he may settle in South Dakota.

A superPAC supporting Osborn — and formed by a former McConnell campaign manager — has attempted to portray Sasse as a "liberal" supporter of President Obama's health care law by taking comments he made at a 2010 health care summit out of context.

But the harshest ad was released recently by the 60 Plus Association, in which three veterans questioned Osborn's fitness for office because of a memo his campaign circulated that lauded his actions in landing a disabled Navy spy plane in China in 2001.

It turns out that the unsigned memo, on Navy letterhead, was written as a favor to Osborn, the Omaha World Herald reported, by a friend working at the Pentagon.

Backlash to the ad, which echoed attacks on John Kerry's decorated service during the Vietnam War, prompted Sasse to issue a statement about what he termed the "counterfeit memo."

He said: "We have nothing but respect for those who serve our country in the military, decry all attacks on Shane's service, and have repeatedly thanked him for his service to our country."

There's little reliable polling in the race, though Sasse looks to be the candidate to beat. Dinsdale, however, appears to have an unexpected opening. Once considered an also-ran, he could tap into a vein of voters fed up with the nastiness and has plenty of his own money to spend. Last week, in a telling move, the 60 Plus Association shifted its attacks from Osborn to Dinsdale.

Erick Erickson of the RedState blog has predicted that a Sasse win in Nebraska " could re-energize conservative efforts and give them hope."

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