Tea party takes on Mitch McConnell in Nebraska Senate race

This article was updated at 2:00 p.m.

The battle of the Republican establishment versus the tea-party all stars will go for another round in Tuesday's Nebraska Senate primary - that is, unless the candidate who has been riding in third place manages to pull off an upset.

As in last week's primary contest for North Carolina's Senate, the race has become a proxy war that has pitted the two wings of the party against each other. It has also meant that money has flooded into Nebraska's relatively cheap media market, with outside groups spending an excess of $3 million to support or oppose the top three candidates, according to the Center for Responsive Politics.

In terms of monetary support and a star-studded list of endorsements, the winner has been front-runner Ben Sasse, the president of Midland University and a former Bush administration official. Sasse has raised $2.5 million, the most of any candidate, and seen groups spend $1.4 million supporting his candidacy. Just shy of $300,000 has been spent to oppose him.

The list of Sasse's endorsements reads like a who's-who list of national conservative politics. Sens. Ted Cruz, R-Texas, and Mike Lee, R-Utah have endorsed him, as have Rep. Paul Ryan, R-Wis., and former Alaska Gov. Sarah Palin. Three of the biggest outside conservative groups - Freedomworks, Tea Party Patriots and the Senate Conservatives Fund - have also been on hand with money and ads.

But it's hard to portray Shane Osborn, the former state treasurer as an establishment pick, even though he has support (although not a formal endorsement) from Senate Minority Leader Mitch McConnell, R-Ky. McConnell is officially neutral in the race, but a Super PAC called Freedom Pioneers Action Network - which was started by his 2008 campaign manager, Justin Brasell - is involved. The group has spent $103,526 supporting Osborn's campaign and $207,052 opposing Sasse, putting it among the top five outside groups putting money into the race.

McConnell's official position is still neutrality. "Nebraska has outstanding Republican candidates to choose from and Sen. McConnell looks forward to congratulating whoever wins this evening," said Josh Holmes, a senior adviser to McConnell.

Many of the local tea parties have also chosen to support Osborn, and more than 50 smaller conservative and grassroots groups from the area penned a letter objecting to the portrayal of Sasse as "the choice of conservative, libertarian, and tea party movement activists and group leaders in Nebraska."

The tone of the campaign has been highly negative overall, and Osborn has seen more money by outside groups to oppose him ($488,548) than support him ($267,172). He has raised just $1.7 million, the lowest total of the top three candidates.

That's where Sid Dinsdale comes in. Once the occupant of the third-place slot in the race to replace the retiring Sen. Mike Johanns, R-Neb., Dinsdale has surged in recent weeks and is poised to come in second, if not pull off an overall upset. There is very little reliable polling in the race, but what is available shows Osborn falling to about 20 percent support as Dinsdale comes up to the mid-20 percent range. Sasse continues to retain a commanding lead, nearing 40 percent in a Magellan Strategies poll taken last week.

In a sign of nerves, two outside groups that back Sasse - the 60 Plus Association and the Club for Growth - have begun running ads to attack Dinsdale in recent days, the Wall Street Journal reports.

Dinsdale has used his own wealth to fund part of his campaign and has raised $1.9 million. No outside groups have stepped in to support him, but nearly $600,000 has now been spent to oppose his campaign.

If Dinsdale does pull off a last-minute victory, it would mimic the 2012 win of now-Sen. Deb Fischer, R-Neb., who overcame the two front-runners in the last race to pull off a last-minute victory. The winner of Tuesday's primary will almost certainly be the next senator given Nebraska's heavy Republican tilt.

Dinsdale and Osborn have both pledged their support to McConnell, the Wall Street Journal reported earlier this week. Sasse finally did so on Election Day when he was asked in an interview on MSNBC's "Daily Rundown" if he would support the minority leader.

"You know, we've said from the beginning of this race that the voters of Nebraska get to make their choice today, and we don't deal with speculative stuff, a little out in front. But obviously, I'm for better conservative ideas and more winsome persuasion and getting to a majority, so obviously I'm a team player and looking forward to support whoever our leader is," he said.

He also downplayed the idea of the election serving as a battleground for an internal GOP war.

"I mean, the national media loves the idea of playing up this intra-Republican Party kinda civil war stuff, but it's just not what Nebraskans are talking about on the ground. It's been pretty overblown in our race," he said.

Johanns, the retiring senator, has not endorsed a successor, but did bemoan the slew of negative ads that have run in the state in a conference call with reporters last week, according to the Nebraska Watchdog.

There is also a primary election in West Virginia Tuesday, but the race has drawn far less attention. Republican Rep. Shelley Moore Capito and Democratic Secretary of State Natalie Tennant are expected to win their respective contests to face off in November to replace retiring Sen. Jay Rockefeller, D-W.Va.