Donald Trump’s overtures to the gay community and policy proposals on gun control in recent days have unnerved and confused some would-be allies and put the presumptive Republican presidential nominee at risk of alienating core GOP constituencies.

Since Sunday’s mass shooting at a gay nightclub by a man claiming allegiance to terror groups, Mr. Trump has pronounced himself an advocate for gays and said on Twitter that he plans to meet with the National Rifle Association to discuss “not allowing people on the terrorist watch...