Could a liberty Republican have won in North Carolina?

Republicans are on the cusp of a Senate majority, their first since 2006. Barack Obama could face an entirely GOP-controlled Congress for the final two years of his presidency.

(Final two years of his presidency—doesn’t that sound good?)

As I write this, the Washington Post’s Election Lab gives Republicans a 76 percent chance of taking the Senate. The New York Times’ model has the likelihood of a Republican Senate at 67 percent. And Nate Silver’s FiveThirtyEight pegs it at 60 percent.

The Washington Post ran this headline Monday: “The odds of Republicans winning the Senate are growing.”

Yet there seems to be one major outlier: Republican Thom Tillis remains behind in his race to unseat North Carolina Democratic Sen. Kay Hagan.

Tillis trails Hagan in the recent major polls and is 3.5 percentage points behind in the Real Clear Politics polling average. Two September polls—one from Fox News, the other from Rasmussen—show him winning less than 40 percent of the vote.

Hagan was thought to be one of the Democrats’ most vulnerable incumbents at the beginning of the year. Right now, she has a better chance of being reelected than Mark Pryor in Arkansas or Mary Landrieu in Louisiana.

Landrieu in particular has survived a number of close calls over the years.

So why is Hagan ahead? This isn’t Jesse Helms’ North Carolina anymore—and even when it was, Helms faced some tough reelection fights—and the state is less reliably red than it once was.

Obama carried North Carolina in 2008. Mitt Romney barely won it in 2012. That year, the Democrats held their national convention in Charlotte.

The Research Triangle and other more liberal parts of North Carolina are growing, at the expense of the state’s more traditional conservative constituencies.

It’s similar to the dynamic that has turned Virginia into a purple state, thanks to the growth of the Northern Virginia suburbs. (Virginia’s incumbent Democratic senator, Mark Warner, is a heavy favorite for reelection.)

But maybe North Carolina Republican primary voters miscalculated when they nominated Thom Tillis, not even forcing him into a runoff election.

Tillis was seen as the safe choice. He was certainly the establishment’s pick.

During the primary, the New York Times described Tillis as “a Republican state lawmaker — supported by the U.S. Chamber of Commerce and $1 million from Karl Rove’s American Crossroads group —standing up for the party establishment.”

Rove famously doesn’t want wacky tea party candidates spoiling the Republicans’ chances. (Though he does want Tea Party supporters to give his preferred candidates more money.)

Tillis seems to be suffering from an enthusiasm gap. I haven’t seen any data on how much the conservative base is supporting him, but a Fox poll earlier this month showed Tillis getting just 45 percent of the white vote, a heavily Republican demographic.

Romney won 68 percent of the white vote en route to eking out a 50.4 percent overall majority in the state two years ago.

There is also a Libertarian Party candidate drawing as much as 7 percent of the vote, potentially part of a recent trend of swinging close Senate races.

Tillis faces the typical Republican establishment problem. The GOP-controlled state legislature in which he is a leader is too conservative for some voters. But the candidate isn’t conservative enough for other voters.

Notice how Tillis had to slink away when Jeb Bush came to endorse him—and started talking about the wonderfulness of Common Core and amnesty.

That will rally the base!

North Carolina Republicans had another alternative. Greg Brannon wasn’t perfect. But as a liberty Republican, he might have been able to change the usual partisan script.

Imagine a North Carolina Senate candidate who was able to effectively raise the issues of war and civil liberties against the Democratic incumbent. Or a Republican who could ask why Congress hasn’t voted on the latest intervention in Iraq and Syria.

Brannon also would have been a candidate who couldn’t be confused for a Common Core backer. And he might have won some of those votes now going to the Libertarian.

Instead primary voters—likely including some conservatives who were probably closer to Brannon than Tillis on the issues—decided it was too risky to chance another Tea Party disappointment with the Senate on the line.

Hagan could still lose. She’s below the crucial 50 percent threshold for an incumbent. Republicans could run the table, or nearly run the table, in the competitive Senate races.

Rand Paul, who supported Brannon during the primary, is campaigning for Tillis.

But right now, at least, the safe bet in North Carolina doesn’t look like the right one.