About three hours after former President Donald Trump was nearly assassinated, on a Saturday evening in mid-July, Robert F. Kennedy Jr. got a phone call: Would he consider joining forces with Trump? What about serving as his running mate?

The caller was Calley Means, a health care entrepreneur who had advised Kennedy on chronic disease policy. He suggested that it might be a moment for unity — Trump had just narrowly escaped the same fate that had befallen Kennedy’s father and uncle. Kennedy, who was running an independent campaign for president, said he wasn’t interested in the vice presidency, and the call ended.

A short while later, Kennedy called back. Yes, he said, he would speak with Trump.