His Teflon vest has worked well for quite a long time.   He's had a target on his back since June of last year and the other 16 Republicans are all gone.  

The March 2016 figure on anti-Trump spending, according to ABC News and numerous other sources  was $63 million.   "The total haul aimed at blocking the real estate mogul is now three times as much as what Trump has spent on his whole campaign and twice as much as the behemoth super PAC Right to Rise spent during its tenure supporting Jeb Bush."