Independent presidential candidate Robert F. Kennedy Jr. called on President Biden to take a “no-spoiler” pledge with him that, if accepted, would lead to one of the two men dropping out of the presidential race in mid-October. Mr. Kennedy ‘s pledge would include a 50-state poll co-funded by Mr. Kennedy and Mr. Biden in mid-October with more than 30,000 likely voters. The survey would test the results of head-to-head matchups between Mr. Biden and former President Donald Trump , the presumptive