Before the 12th amendment, the presidential candidate who got the second most electoral votes became the vice president. This meant they were usually different parties.
It occurred to me that one thing this achieved was always ensuring that there was someone in the room who would be willing to disagree with the president. He couldn’t surround himself with yes-men.
That’s kind of my point though. Even with the utter incompetence of Trump’s administration eroding security, they still couldn’t get an easy shot. Iran has had a big bounty on Trump’s head for years and nothing.