An independent presidential candidate, Robert F. Kennedy Jr., threw his support behind President Trump Friday during a speech at Phoenix, and said he is suspending his campaign and taking his name off the ballot in 10 critical swing states that will likely decide the election.

The Kennedy scion, though, is not dropping out of the presidential race or taking his name off the ballots in states that are solidly red or blue. He is encouraging supporters in those states to vote for him. He just says he can’t ask his staff, donors, or volunteers to spend any more time or money on a campaign that doesn’t have a “realistic path to victory.”

“By staying on the ballot in battleground states, I would likely hand the election over to the Democrats,” Mr. Kennedy said. “I want everyone to know that I am not terminating my campaign, I am simply suspending it.”

Mr. Kennedy also announced in his speech, which was live-streamed to more than 1.5 million viewers on X, that he is joining forces with Trump to create what he calls a “unity ticket,” under which Mr. Kennedy would play a role in a Trump administration in helping to solve what Mr. Kennedy calls the “childhood disease epidemic.” This issue has been central to the Kennedy campaign — his at-times controversial vaccine positions — and it has attracted much of his base of support.

“We talked about Abraham Lincoln’s Team of Rivals,” Mr. Kennedy said of his “unity party” talks with Trump. “That arrangement would allow us to disagree publicly and privately and fiercely if need be, on issues over which we differ, while working on the existential issues upon which we are in concordance.”

Mr. Kennedy called the decision to endorse Trump “heart-wrenching,” but said Trump is the “best hope.” 

“We are aligned with each other on the key issues, like ending the forever wars, ending childhood disease epidemics, securing the border, protecting free speech, unraveling corporate capture of our regulatory agencies,” Mr. Kennedy said, adding a few more points, among them protecting elections.

The announcement comes one day after the Kennedy campaign filed paperwork to remove its name from the Arizona ballot. Trump is polling ahead of Vice President Harris in Arizona by 0.2 percent, according to the Real Clear Politics average, and recent polling suggests Mr. Kennedy is pulling more votes from Trump than Ms. Harris.

Fighting for every last vote is what prompted Trump and Mr. Kennedy to court Libertarians at the party’s convention in May. In 2020, Mr. Biden won Arizona by just more than 10,000 votes, while the Libertarian Party’s candidate, Jo Jorgenson, earned more than five times that number. Trump won Arizona in 2016 by 90,000 votes, while the Libertarian Party candidate earned more than that. Third-party votes in Wisconsin and Georgia also helped decide the election in 2020.

Mr. Kennedy was running the most successful third-party presidential campaign since Ross Perot in 1992. His poll numbers, though, fell precipitously to around 5 percent support after Mr. Biden dropped out of the race and Ms. Harris replaced him.

By keeping his name on the ballot, Mr. Kennedy may be hoping he collects more than 5 percent of the vote and can earn “minor party” status from the Federal Elections Commission. With that status comes limited public funding. Mr. Kennedy has said that exposing the rigged system against third-party candidates and building an independence movement are critical to him.

“The movement continues if he does that,” the outreach director for American Values PAC, Larry Sharpe, said in a livestream on X Thursday about keeping Mr. Kennedy’s name on the ballot in a majority of states.

The Sun spoke with several Kennedy supporters just before the announcement about whether they would vote for Trump if Mr. Kennedy dropped out of the race. Those on the right and those who identified as libertarian said they would. Those on the left said they would if Mr. Kennedy endorsed Trump or got a seat in a Trump administration.

“I guess I’m going to have to vote for Trump,” a manager at an environmental organization, who has never voted Republican, tells the Sun. “I believe so much in Bobby Kennedy.”

“That would probably steer me in that direction,” a Manhattan sobriety coach tells the Sun. “But I wouldn’t tell anyone I voted for Trump.”

“This is good news for President Trump and his campaign – plain and simple,” a Trump campaign press release Friday said.