Another potential Republican candidate for president has waded into North Carolina's competitive Republican Senate primary with an endorsement.

Former Florida Gov. Jeb Bush offered his stamp of approval Thursday for Thom Tillis, who leads his party's field heading into next week's primary contest.

“Thom Tillis is a proven conservative leader with an impressive track record of results for North Carolina businesses and families,” Bush said in a statement. “His work on key issues like improving education, keeping taxes low and eliminating burdensome regulations is a testament to his leadership as North Carolina’s House Speaker."

"It is critically important that Republicans win a majority in the U.S. Senate," Bush added, "and I am confident that the road to a majority runs through Thom Tillis in North Carolina.”

Although Tillis is favored to take on Democratic Sen. Kay Hagan in the general election, in one of this election cycle's most important Senate races, he will need to win 40 percent of the vote in Tuesday's primary election to avoid a run-off with the second-place Republican. A run-off would extend an already-costly primary for two months into July.

Bush's endorsement will no doubt offer a last-minute boost to Tillis, who has also attracted support from the U.S. Chamber of Commerce and the Karl Rove-backed group American Crossroads, which spent $1.6 million on television ads backing Tillis during April.

But there are also powerful forces at work against Tillis. A Libertarian candidate, Greg Brannon, has been endorsed by Sen. Rand Paul, R-Ky., who this week told Politico he plans to campaign for Brannon in North Carolina on Monday. And Mark Harris, a Baptist pastor, is backed by former Arkansas Gov. Mike Huckabee, another 2016 Republican contender who appeals to the religious right, and the social-conservative Family Research Council.

In most public polls to date, Tillis has neared, but not exceeded, the 40-percent threshold he would need to meet to avoid a run-off.