LIVE: RFK Jr. to drop out of presidential race | FOX 4

Independent presidential candidate Robert F. Kennedy Jr. is expected to announce his exit from the 2024 race at a news conference Friday afternoon in Phoenix.

Kennedy Jr., a son of former Attorney General Robert F. Kennedy and a nephew of former President John F. Kennedy, hasn’t disclosed the reason for his Friday remarks, only noting that it’s "about the present historical moment and his path forward."

But Kennedy’s campaign momentum has slipped in recent weeks – and he withdrew from the ballot in Arizona late Thursday, despite submitting well more than the required number of signatures to appear on the ballot, according to the Associated Press.

There’s also speculation that he may throw his support behind former President Donald Trump. Trump is holding a rally in neighboring Glendale, Arizona, just hours after Kennedy’s event.

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 his administration if Kennedy drops out and endorses him.

When he called into Fox News Channel after the Democratic National Convention wrapped Thursday night, Trump said of Kennedy, "I have no idea if he’s going to endorse me."

But he noted that they were going to be in the same state and said, "It’s possible we will be meeting tomorrow and we’ll be discussing it."

It’s unclear how big of a boost Trump could get from Kennedy’s endorsement, though polls show Kennedy’s staying in the race would hurt Trump more than Vice President Kamala Harris, the Democratic nominee. 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%).

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.

But the two campaigns have ramped up their compliments to each other and engaged in behind-the-scenes discussions in recent weeks, sources told the AP.

Nicole Shanahan, Kennedy’s running mate, also openly suggested on a podcast this week that his campaign might "walk away right now and join forces with Donald Trump."

Kennedy first 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 a third-party bid, fueled in part by anti-establishment voters and vaccine skeptics who have followed his anti-vaccine work since the COVID-19 pandemic.