How hard? A STINGER?
Iranians haven't been able to smuggle so much as a tin of caviar here since 1979. What, one is gonna just waltz down the beach with a stinger? And al Queda and the Taliban and ISIL are also gonna hit some presidents too one day on a day that isn't today.
To this day, the official word about the bombing of Pan Am Flight 103 over Lockerbie, Scotland (I said 101 before, my bad) is that it was Libya's doing, even naming, arresting, & convicting those who were responsible. But everyone still believes Iran was behind it. The fact that our gov't never once suggested they were connected ironically is a sort of proof, because anyone cuts a fart in the region and it's blamed on Iran. 9/11 was they only other thing not automatically blamed on Iran, but Bush couldn't later resist from calling Iran part of the "Axis of evil," and this after they gave us valuable intel used to invade Afghanistan.
Anyways, the Lockerbie bombing would be more Iran's style. A hit widely believed to be them, but no proof.
As for trying to get at Trump - in addition to being suicide for Iran - every last Persian rug within 100 miles of him is under heavy scrutiny. Just not going to happen.