Robert F. Kennedy Jr. withdrew from the ballot in Arizona late Thursday, a day before he and Donald Trump were set to appear miles apart in the Phoenix area as speculation grows that Kennedy could drop his independent presidential bid and endorse the Republican nominee.

Kennedy is scheduled to speak in Phoenix at 11 p.m. Pacific time “about the present historical moment and his path forward,” according to his campaign. Hours later, Trump will hold a rally in neighboring Glendale.

Trump, campaigning Thursday in southern Arizona at the U.S.-Mexico border, said that “no plans have been made” for Kennedy to appear with him Friday. But he noted they would be in the Phoenix area at the same time.

On Thursday evening, Trump’s campaign made an unusual announcement, teasing that he would be joined by “a special guest” at his Glendale event.

Hours later when he called into Fox News Channel after the Democratic National Convention wrapped, Trump said of Kennedy, “I have no idea if he’s going to endorse me.”

But, after noting that they were going to be in the same state, added, “It’s possible we will be meeting tomorrow and we’ll be discussing it.”

Representatives for Trump’s campaign did not respond to messages about whether Kennedy would be the guest, and the Kennedy campaign did not immediately return a message seeking comment if he would be joining Trump.

Kennedy’s Arizona withdrawal, confirmed by a spokesperson for the secretary of state, came less than a week after Kennedy submitted well more than the required number of signatures to appear on the ballot. His critics raised questions about the validity of some of the signatures after a pro-Kennedy super PAC was heavily involved in his effort to collect them, potentially running afoul of rules against coordination between candidates and independent political groups.

But Thursday, Kennedy, his running mate, Nicole Shanahan, and all of their electors submitted notarized letters dated that day withdrawing from the Arizona ballot.

A year ago, some would have thought it inconceivable that Kennedy — a member of the most storied family in Democratic politics — would work with Trump to keep a Democrat out of the White House. Even in recent months, Kennedy has accused Trump of betraying his followers, while Trump has criticized Kennedy as “the most radical left candidate in the race.”

But the two campaigns have ramped up their compliments of each other and engaged in behind-the-scenes discussions in recent weeks, according to those familiar with the efforts. Both campaigns have spent months accusing Democrats of “weaponizing” the legal system for their own benefit. And both have hinted publicly that they could be open to joining forces, with the shared goal of limiting the election chances of Democratic presidential nominee Kamala Harris.

Last month, during the Republican National Convention, Kennedy’s son posted and then quickly deleted a video showing a phone call between Kennedy and Trump, in which the former president appeared to try to talk Kennedy into siding with him.

Talks between the two camps have continued, with close Trump allies quietly lobbying Kennedy to drop out of the race and support the Republican nominee, according to a person familiar with the efforts who spoke on condition of anonymity to discuss private conversations.

Trump told CNN on Tuesday that he would “love” an endorsement from Kennedy, whom he called a “brilliant guy.” He also said he would “certainly” be open to Kennedy playing a role in a prospective Trump administration if Kennedy drops out and endorses him.

Shanahan also openly suggested on a podcast this week that the campaign might “walk away right now and join forces with Donald Trump.” While she clarified that she was not personally in talks with Trump, she entertained the idea that Kennedy could join Trump’s administration as secretary of the Department of Health and Human Services.

“I think that Bobby in a role like that would be excellent,” Shanahan said. “I fully support it. I have high hopes.”

Kennedy, a son of former Atty. Gen. Robert F. Kennedy and a nephew of former President John F. Kennedy, hasn’t disclosed the reason for his Friday news conference, but it comes as his campaign’s momentum has slipped.

Kennedy Jr. entered the 2024 presidential race as a Democrat but left the party last fall to run as an independent. He built an unusually strong base for an indepdendent bid, fueled in part by anti-establishment voters and vaccine skeptics who have followed his anti-vaccine work — often propagating debunked theories— since the COVID-19 pandemic. But he has since faced strained campaign finances and mounting legal challenges, including a recent ruling from a New York judge that he should not appear on the ballot in that state because he listed a “sham” address on nominating petitions.

Recent polls put his support in the mid-single digits. And it’s unclear if he’d get even that in a general election, since third-party or independent candidates frequently don’t live up to their poll numbers when voters cast their ballots.

There’s some evidence that Kennedy’s staying in the race would hurt Trump more than Harris. According to a July AP-NORC poll, Republicans were significantly more likely than Democrats to have a favorable view of Kennedy. And those with a positive impression of Kennedy were significantly more likely to also have a favorable view of Trump (52%) than Harris (37%).

In an interview with MSNBC at the Democratic National Convention in Chicago on Thursday, Harris communications director Michael Tyler said her campaign welcomes Kennedy voters should the independent candidate drop out.

For voters who see Trump as a threat, who are looking for a new way forward, or who want “government to get the hell out of the way of their own personal decisions, there’s a home for you in Kamala Harris’ campaign,” Tyler said.

For Trump, Friday will mark the end of a week’s worth of battleground state visits in which he has sought to draw attention away from Democrats’ celebration of Harris’ presidential nomination in Chicago.

He traveled to Pennsylvania, Michigan, North Carolina and Arizona’s U.S.-Mexico border for events billed as focusing on the economy, crime and safety, national security and the border. He will close out the week Friday with stops in Las Vegas and Glendale, Ariz.

Cooper and Swenson write for the Associated Press. AP writers Jill Colvin in New York, Michelle L. Price in Phoenix, Meg Kinnard in Chicago and Linley Sanders in Washington contributed to this report.