The GOP Senate primary in Nebraska will be a 2014 battlefield in the hot war between the Republican establishment and the Tea Party insurgents. But at first glance, it's hard to see a casus belli.

State Treasurer Shane Osborn is a conservative Republican who rails against Washington insiders and criticizes the Republican leadership for the recent budget deal, but whose pedigree shows strong ties to the Republican establishment.

Former Bush administration official Ben Sasse is also a conservative Republican who rails against Washington insiders and criticizes the Republican leadership for the recent budget deal, but whose pedigree shows strong ties to the Republican establishment.

Looking at their records and their rhetoric, you wouldn't be able to tell which is the candidate of the Tea Party and which is the candidate of K Street and the GOP establishment. But their donor lists make it crystal clear.

The Club for Growth and the Senate Conservatives Fund are backing Sasse. Perhaps for that reason, K Street and the GOP establishment are bankrolling Osborn.

A few dozen corporate lobbyists are hosting a Feb. 4 fundraiser for Osborn at the National Republican Senatorial Committee headquarters. The host list is a roster of the GOP establishment. Also, the lobbying agendas of some of Osborn's backers shows why the conservative grassroots has grown increasingly hostile to the business lobby.

Wayne Berman and Charlie Black headline Osborn's D.C. fundraiser. The two K Streeters are pillars of the GOP establishment. They backed Texas Lt. Gov. David Dewhurst over Ted Cruz in 2012. And they supported governor-turned-health-secretary-turned-lobbyist Tommy Thompson over two Tea Partiers in a heated Wisconsin primary that same year.

Lobbyist Rick Murphy, who threw a fundraiser for Dewhurst last cycle, is also on Osborn’s host list.

So is Billy Piper, who was Senate Minority Leader Mitch McConnell’s chief of staff from 2002 to 2010. Today, he’s a lobbyist at the K Street firm Fierce, Isakowitz and Blalock. Also on the host list are Piper's boss Kirk Blalock and colleague Kate Hull.

When you check out Piper, Blalock and Hull’s lobbying resumes, you see why the K Street wing can’t find peace with the conservative base. Blalock's firm pocketed about $1.5 million lobbying for government-sponsored enterprise Fannie Mae from 2002 until the company collapsed into federal conservatorship in 2008. Federal filings show Blalock lobbying for Fannie on “GSE Reform,” which means he lobbied (successfully) against Republican efforts to rein in Fannie’s unsustainable inflation of the housing bubble.

Blalock lobbied for Obama's stimulus on behalf of the windmill lobby, the American Wind Energy Association. Blalock and his firm also lobbied for wind-energy subsidies and federal rules forcing utilities to buy wind-generated power.

Kraig Siracuse used to be a staffer for former Sen. Al D'Amato and the Senate Appropriations Committee's Subcommittee on Defense, led by Republican appropriator Ted Stevens. Now, he’s an appropriations lobbyist raising money for Osborn.

Osborn isn’t running as a porker or a corporatist. His campaign tells me he opposes climate-change regulation, the death tax and earmarks.

Why, then, is K Street so solidly on Osborn’s side?

“I want a guy who can work within the system and get half a loaf,” Siracuse tells me. “If I can get half a loaf on the conservative side, that’s better than what we’re getting now.”

Siracuse, a self-identified conservative, knows Osborn through their joint Navy background, and he credits Osborn for helping bring down spending in the Cornhusker State. Siracuse paints Sasse as impractical, pointing to his call to move the U.S. capital to Nebraska.

Another K Streeter tells me he’s backing Osborn because of “the way he looks at issues. He takes a principled approach, but a very practical approach about policy that is going to affect growth and job creation.”

But the real reason K Street is behind Osborn might be more parochial: The Senate Conservatives Fund is backing Sasse. The SCF got behind Sasse just before it entered an all-out war with McConnell by endorsing McConnell's primary opponent Matt Bevin.

Sasse supporters tell me that this schism has made business lobbyists afraid to support anyone backed by the SCF. Medical device lobbyists canceled a Sasse fundraiser after the SCF-McConnell war flared up, a Sasse ally told me.

Once Tea Partiers start lining up on one side and K Streeters on the other, this pattern reinforces itself. The result: One conservative Nebraskan has become the insurgent candidate, and the other has become the establishment candidate.

Chalk it up to the fog of the GOP civil war.

Timothy P. Carney, the Washington Examiner's senior political columnist, can be contacted at His column appears Sunday and Wednesday on