It was inevitable that the field of primary challengers to Lindsey Graham would grow, but the sheer number of ambitious Republicans seeking to oust the South Carolina senator may end up being the undoing of them all.

With a new opponent entering the race over the weekend and another poised to join soon, the question is whether enough variables could fall into place to cause a different result this time.

It’s possible, according to several South Carolina GOP operatives who spoke with CQ Roll Call in recent days. But it would take an extraordinarily large amount of money, extensive support from outside groups and an unlikely coalescing of the anti-Graham vote. A top challenger would need all of those things, plus cash to spare for a runoff.

“The thing we’ve learned with Sen. Graham is, unlike a lot of incumbents, he doesn’t take much for granted,” said Charleston-based consultant Adam Temple. “He’s kind of always poised to run a difficult race.”

Republican operatives said Graham’s chances for re-election remain good as long as Nancy Mace, former congressional candidate Richard Cash and state Sen. Lee Bright, who’s reportedly set to enter the race soon, duke it out in an effort to finish second. If Graham is held under 50 percent, the top two will advance to a runoff.

“If the groups like FreedomWorks, Club for Growth and Americans for Prosperity coalesce around someone like Nancy, we’ve seen some pretty big incumbents get beaten, and I don’t think that’s outside of the realm of possibility,” said Dan Tripp, a consultant and former state legislator.

The second-term senator has faced a primary challenger amid conservative criticism before, dispensing of one in 2008 by taking two-thirds of the vote.

This cycle, Graham set a new personal fundraising record in the second quarter, raising $1.4 million for the first time ever over a three-month period. He ended June with $6.3 million in the bank, already enough to saturate the state’s media markets in the months leading up to the June primary.

One unaffiliated GOP operative in the state said the anti-incumbent vote that almost any challenger starts out with in a statewide race in South Carolina is about one-third of the electorate.

“The problem for any opponent taking on an incumbent … is getting from 35 percent to 50 percent plus one,” the operative said. “That’s where it gets real expensive.”

Graham’s leadership on the immigration overhaul that the Senate passed this year and his penchant for working with Democrats on various issues has left him vulnerable to an ideological primary challenge. Hoping to take Graham out next year are at least three Republicans with varying degrees of campaign experience and the potential to splinter the anti-Graham messaging.

The most intriguing of the bunch is Mace, a consultant and the first woman to graduate from the Citadel. She’s been publicly critical of Graham for some time but just entered the race on Aug. 3 with an address to the Berkeley County Republican Party.

“What Nancy Mace brings to the race is the most legitimate challenger in a primary that Sen. Graham has had to date,” Temple said. “She’s obviously going to appeal to a lot of the Republicans in the state who are disgruntled with how Sen. Graham has voted with Democrats.”

In a statement to CQ Roll Call, Graham spokesman Tate Zeigler said the senator “is a strong fiscal, social, and national security conservative with the record to back it up.” Among other things, Zeigler cited Graham’s support for repealing the health care law, “standing up for the unborn, protecting the second amendment” and ensuring the country has a strong military.

Not only must the groups coalesce around a single candidate, but they’ll likely need to invest a potentially unprecedented amount of money to come close to keeping pace with Graham, sources said.

The Republican operative, speaking on background, said the only way Graham could fall below 50 percent in the primary is if a candidate or group “can do two to three months of full saturation television in every market in this state” — potentially a $3 million proposition.

Tripp said Graham became a “rock star” to the Republican base in the late 1990s when, while serving in the House, he was part of the group that sought to oust Speaker Newt Gingrich and was one of the impeachment managers of President Bill Clinton.

Now, Tripp said, “he doesn’t seem to have a problem poking the eye of conservative voters and working on issues that are diametrically opposed to where conservative voters stand.”

For Graham’s primary problems to escalate, he’ll need to lose the support of more than just a wing of the primary electorate. And at this point, there’s no evidence that’s happened.