With Mitch McConnell pulling away from Matt Bevin in Kentucky and Thad Cochran holding a double-digit lead in Mississippi (although the last poll there was taken over a month ago), tonight might be the last chance for grassroots righties to score a Senate primary win this cycle. Ben Sasse’s led in each of the last three polls in Nebraska and his lead’s gotten bigger each time. Beltway Republicans are now sufficiently glum about stopping him that they’ve resorted to pre-spin as lame as this:

Those framing #NEsen as tea party vs establishment referendum are trying to exploit conservatives. It isn't. May the best candidate win.

— Brad Dayspring (@BDayspring) May 13, 2014

Anyone calling the #NESen primary a "tea party vs establishment" fight clearly hasn't been following the race – at all.

— Brian Walsh (@brianjameswalsh) May 13, 2014

Sasse’s a favorite of right-wing groups like the Senate Conservatives Fund, which is precisely why establishment types wanted to beat him. It’s not that he’s the second coming of Ted Cruz, it’s that those groups are a threat potentially to GOP incumbents everywhere and squashing them across the board this cycle might have neutralized that threat. With no wins to show their donors, tea-party PACs might have seen their funding dry up. As it is, they’ll probably have a nice victory by Sasse tonight to showcase going forward.

Emphasis on “probably.”

For months, [Shane] Osborn and Sasse all but ignored the other GOP candidates in the race as they engaged in a head-to-head showdown for the likely right to succeed outgoing Sen. Mike Johanns in the heavily Republican state.

With the frontrunners battling it out at the top of the polls, outside groups allied with both men became immersed in a brutal game of one-upmanship, launching negative ads that became increasingly personal. But more than a few state Republican voters appear to have been so turned off by the spectacle that they began to look for other options.

With the arrival of Primary Day, the toxic tone that defined the race has provided a surprising opportunity for the partially self-funded [Sid] Dinsdale to swoop in and become a legitimate contender.

Recent public polling has been scare, but interested parties agree privately that Dinsdale’s late surge is real. To find evidence that his rivals are taking the new threat seriously, look to the Nebraska airwaves.

Something like that happened in the last Nebraska Senate primary, when Jon Bruning and Don Stenberg pounded each other while Deb Fischer quietly moved up the polls until finally surging ahead down the stretch. A month ago Dinsdale was in third place, more than 10 points behind the second-place Osborn. As of last week, he was in second place and as many as seven points ahead of Osborn, and possibly closing in on Sasse. That’s the real suspense tonight — not whether Sasse can hold off Osborn but whether he can hold off the businessman Dinsdale. Judging by this response from Mitch McConnell’s camp to Sasse’s peace offering this morning, it sounds like they think he can. An unnamed McConnell ally told NRO that Sasse is a “very practical conservative who’s more interested in achieving the right policy outcome than engaging in a quixotic civil war with his own party.” Sounds like something you’d say of a man you expect to be working with soon.

The Nebraska polls close at 9 p.m. ET. Here’s the Nebraska Secretary of State’s elections page for following the Senate results.