Robert F. Kennedy Jr. accidentally reveals who he's endorsing for president moments before he's expected to drop OUT of race

A court filing beat Robert F. Kennedy Jr. to the punch. 

In Pennsylvania, the independent candidate put in writing that he planned to endorse Republican nominee, former President Donald Trump, according to the Associated Press. He also requested to be removed from Pennsylvania's ballot.  

The news broke as journalists waited for the candidate to speak Friday in Phoenix where RFK Jr. is expected to drop out of the race after withdrawing Thursday night from Arizona's ballot. 

Trump is speaking in nearby Glendale later Friday and his campaign teased a 'special guest' would join him onstage. 

That guest was largely believed to be Kennedy, as Trump has courted the independent's endorsement for weeks. 

Kennedy went scorched earth on the Democratic Party in his Phoenix remarks. 

'I began this journey as a Democrat, the party of my father, my uncle, the party I pledged my allegiance to long before I was old enough to vote,' he reminded the crowd. 

 Kennedy then blasted the Democratic Party for 'canceling the primary to conceal the cognitive decline of the sitting president.'

Kennedy's running mate, Nicole Shanahan, cast some doubt Friday that it would happen, telling podcast host Adam Carolla that Trump needed to apologize for his COVID-19 response. 

'The hesitation we have right now in joining forces with Trump is that he has not apologized or publicly come out and said Operation Warp Speed was my fault, was a failure and I let it happen,' Shanahan said. 

Operation Warp Speed was Trump's public-private partnership for the swift development of COVID-19 vaccines.

Trump, rightly, took credit for Operation Warp Speed and he and his allies expressed dismay when the fruits of that labor - Pfizer's announcement that the vaccine prevented more than 90 percent of infections - didn't come out until after Election Day 2020.

Since then, with vaccine skepticism on the rise on the political right, Trump has distanced himself from the COVID vaccine.

Shanahan said Trump needed to apologize for the COVID lockdowns and for keeping Dr. Anthony Fauci as a top adviser too.

'There was a lot that happened under Donald Trump's watch that should not have happened and cannot happen again,' she told Carolla. 'And if we are going to put our bet with him - and we haven't, we have not confirmed anything - we need absolute assurance.'