DAVIDSON, N.C. — In the Republican Senate primary in North Carolina, the national Republican Party and its network of supportive third-party groups have aggressively worked to correct their mistakes from the last election cycle.

No longer is the party content to sit idly by and let the primary play out as it will, as it did in states such as Missouri in 2012, to disastrous effect in the general election. Instead, the Republican establishment isn’t taking any chances on North Carolina, one of the key 2014 battleground states this fall. The GOP has banded together behind a candidate, North Carolina Speaker Thom Tillis, giving him the full support of the party’s fundraising and messaging arms in his challenge to Sen. Kay Hagan, the incumbent Democrat.

Meanwhile, Tillis’ record in the state legislature has passed muster with pro-Republican groups across the ideological spectrum, winning him endorsements from the NRA, National Right To Life and the Chamber of Commerce — “the Republican trifecta,” as one party operative aptly termed it.

So is Tillis a dead cinch in the May primary? Not by a long shot.

Republicans had hoped Tillis would win 40 percent support from the party’s voters, the threshold needed to avoid a run-off. But recent public polling has shown Tillis falling far short, even by double digits — and he will likely face either Greg Brannon, a Libertarian physician, or Mark Harris, a Baptist pastor courting evangelical voters, during a two-month, head-to-head race culminating in a mid-July vote.

Tillis is also being hurt by attack ads underwritten by Democratic groups. “They’re trying to do everything they can at least to force a run-off, but I don’t even believe that’s going to happen,” Tillis told reporters Tuesday following a Republican debate at Davidson College.

Turnout in the run-off election could closely mimic that of a special election, with remarkably low voter participation, possibly hundreds of thousands of votes less than in the first round of primary voting.

“It’s trouble, because it’s much more activist-heavy than even the normal Republican primary,” said one North Carolina Republican operative with ties to Tillis.

In prior election cycles, both parties have engaged in primary politics, but often on the fringes or in the shadows. The high-profile early involvement by both Democrats and Republicans in North Carolina is a new twist, and it has become an important test case as the parties suss out how best to meddle in plain sight.

“It’s an important case because it’s a crowded primary, and clearly there is one candidate in the primary who is the strongest,” said a senior aide to a third-party group backing Tillis. “From our standpoint, the reason we’re involved early is, we want to replace a liberal in Kay Hagan with a conservative in Thom Tillis.”

Democrats are less hopeful of boosting Brannon or Harris to a primary victory than they are “interested in making (Tillis) bleed,” said one party strategist, forcing him to endure attacks from all sides and slog through a prolonged primary.

“It’s either going to be Tillis next month, or it’s going to be Tillis this summer, but he’ll win the nomination eventually,” the strategist reasoned. “Tillis and his coalition of outside groups will just carpet-bomb anyone he ends up against (in the run-off).”

The most prominent Democratic foe to Tillis so far has been the Senate Majority PAC, which, among other things, hit Tillis for once employing two aides who had personal relationships with lobbyists. Hagan, for her part, recently released her campaign’s first advertisement, airing on country music and Christian radio stations, attacking Tillis.

The latest in a string of ads by American Crossroads, the conservative group founded by Karl Rove that has pledged its support for Tillis, has also pointed to Democrats’ early and aggressive meddling — even as American Crossroads has itself purchased $1.6 million in television advertising to boost Tillis in the month leading up to the primary.

“Now, Washington liberals are attacking Tillis — so desperate, they’ll say anything to stop this proven conservative,” said a narrator in the American Crossroads ad, which began airing in the Raleigh and Charlotte media markets on the day of the Davidson debate.

During the debate, the first of three in the span of a week to feature the top Republican contenders, Tillis sounded like the Republican nominee as he focused his fire squarely on Hagan — but his Republican adversaries were not willing to concede the primary just yet. Brannon attacked Tillis’ stances with venom, and Harris argued he would be the most electable versus Hagan.

The two underdog candidates stuck around the lobby long after the debate, working the room. But there was some simmering frustration that, even with the primary likely to continue into the summer, national Republicans weren’t even giving them a chance.

“Instead of the (National Republican Senatorial Committee) recognizing that maybe they had a weaker candidate, suddenly they have begun to feel like they have got to pull out all the stops and call all hands on deck to try to save (Tillis),” Harris said. “While you’ve got Harry Reid trying to interfere in a Republican primary in North Carolina, I’m not so sure you haven’t had the NRSC trying to interfere in a way that maybe is not their place until post-primary.”