The battle between the Tea Party and establishment will play out over several state primaries in the next few weeks. But Tuesday will see the first tug of war in a Senate primary in North Carolina that features the speaker of the North Carolina House Thom Tillis, who is backed by the Chamber of Commerce and Karl Rove's American Crossroads, and two poorly funded candidates supported by the Tea Party - Mark Harris, a Baptist minister, and Greg Brannon.

The Hill:

The establishment favorite looked like he was heading to a runoff until the 11th hour. Just one month ago, Tillis was struggling to pull away in polls and was far below the 40 percent threshold in public polls. He’s avoided also any major errors, giving his opponents few opportunities to attack him.

Tillis’s campaign is preparing to win on Tuesday, though no one will say publicly they’re banking on that outcome.

“We feel we're moving in the right direction and have a good amount of momentum,” Tillis campaign manager Jordan Shaw told The Hill. “We're peaking at the right time. But we're also preparing for any outcome.”

“Tillis has it. People still don't know the other candidates,” said North Carolina politics expert John Davis. 

The race is a top priority for Republicans as they look to win back Senate control, and polls have found a tight race against Hagan in the swing state for months. 

Tillis has been the only GOP candidate with the resources to run a serious advertising campaign. He’s spent more than $1 million in the last month to cement his conservative credentials and push back on attacks coming from Democratic groups, while neither of his opponents has been able to spend significant resources on TV.  

American Crossroads spent more than $1.5 million on ads supporting Tillis in the Charlotte and Raleigh media markets (Tillis concentrated on smaller markets during the same time, effectively blanketing the state in ads), while the U.S. Chamber of Commerce came in with a $750,000 ad buy for the final week of the campaign. Americans for Prosperity has also spent millions attacking Hagan. More than $12 million has already been spent either propping up Tillis or attacking Hagan.

That spending helped put Tillis in a good position to avoid a runoff, according to recent public and private polls. If he avoids one, that’ll allow him to save a lot of money and give him the luxury of turning his full attention to the freshman senator. 

It should be noted that the outside money bought ads that did not target Tillis's conservative opponents, but rather Hagan instead. At the very least, the ads have given Tillis some much needed state-wide name recognition that he was lacking just a month or so ago.

Mr. Brannon is backed by Rand Paul and Mike Lee, as well as Freedom Works. Senator Paul will be in North Carolina to stump for Brannon today.

If Tillis fails to get 40% of the vote, it will give new life to the second place finisher - probably Brannon - and set up real battle for the nomination in the run off election this July. It hardly matters how far behind Brannon is if he gets another shot at Tillis. Recall that Ted Cruz trailed badly at first in his runoff against David Dewhurst, but ended up winning by 14 points.

Critically, if there is a runoff, both the Tea Party and establishment should keep the focus on Hagan and make their case for who is better qualified to defeat her. Savaging each other only plays into the Democrat's hands and will make a winnable race in November a toss up.