A trio of Republican presidential prospects is facing off in North Carolina by throwing their weight behind the top three contenders in the state’s high-stakes GOP primary for Senate.  

Most recently, former Florida Gov. Jeb Bush endorsed the frontrunner , state Speaker Thom Tillis, on Thursday.  

“I am confident that the road to a majority runs through Thom Tillis in North Carolina,” Bush wrote in an email to Tillis supporters.  

A candidate must get 40 percent of the vote  in Tuesday’s primary to avoid a July runoff in the Tar Heel State. The winner will face Sen. Kay Hagan, D-N.C., in one of the most competitive Senate races of the cycle.  Another GOP Senate candidate, Dr. Greg Brannon, will also get some last-minute help in his quest push Tillis into a two-candidate runoff . Sen. Rand Paul, R-Ky., who is openly considering a presidential bid, will travel to the state Monday to campaign with Brannon. Paul endorsed Brannon early on in his campaign.  

The third major contender in the primary, Pastor Mark Harris, has the backing of another Republican who has expressed interest in the 2016 race. Former Arkansas Gov. Mike Huckabee endorsed him.  

The Senate race is rated Tilts Democrat by the Rothenberg Political Report/Roll Call.