The assassination attempt on Donald Trump, President Joe Biden’s departure from the race, Vice President Kamala Harris’ jump to the top of her ticket, two vice-presidential picks and two conventions have all shaken up the election in the last six weeks. Now, independent Robert F. Kennedy Jr.’s possible exit could be the next big event.

His own running mate is talking about weighing whether to drop out, and now his campaign is preparing a big speech on Friday.

Polls show…