Robert F. Kennedy Jr. has announced that he is suspending his independent bid for the U.S. presidency.
He said he would try to keep his name off the ballot in swing states because he believed his presence in the race would help Democratic nominee Kamala Harris.
Mr Kennedy said his supporters could continue to back him in most US states where they were unlikely to influence the outcome of the election.
Late this week, he took steps to withdraw his candidacy in at least two states, Arizona and Pennsylvania.
Mr Kennedy said the move was the result of conversations he had with Donald Trump over the past few weeks.
Ahead of the speech, his campaign said in court filings in Pennsylvania on Friday that it would support Mr. Trump for president.
However, a spokesman for Mr Kennedy said the lawsuit was filed in error.
“Mr. Kennedy did not support President Trump,” said spokeswoman Stephanie Spear.
“The application was filed by an attorney and was not reviewed by campaign representatives.”
She said the documents would be updated.
A year ago, some would have found it unthinkable that Mr. Kennedy, a member of the most storied family in Democratic politics, would work with Mr. Trump to keep a Democrat out of the White House.
Even in recent months, Mr. Kennedy has accused Mr. Trump of betraying his followers, while Mr. Trump has criticized Mr. Kennedy as “the most radical left-wing candidate in the race.”
However, in recent weeks, representatives of both campaigns have begun to exchange compliments and engage in behind-the-scenes discussions more frequently, according to people familiar with the matter.
Both campaigns have spent months accusing Democrats of weaponizing the legal system for their own gain.
And both have publicly hinted that they might join forces for the common goal of hurting Democratic presidential nominee Kamala Harris's election chances.
Mr Trump told CNN on Tuesday that he would “love” to have an endorsement from Mr Kennedy, whom he called a “brilliant guy”.
He also said he would “certainly” be open to Mr Kennedy playing a role in his administration if he declined to participate and supported him.
Mr Kennedy's running mate Nicole Shanahan also openly suggested on a podcast this week that his campaign might “leave right now and join forces with Donald Trump.”
While she clarified that she was not in personal talks with Mr. Trump, she floated the idea that Mr. Kennedy could join Mr. Trump's administration as secretary of the Department of Health and Human Services.
“I think Bobby would be terrific in that role,” Ms. Shanahan said. “I’m all for it. I have high hopes.” The planned remarks by Mr. Kennedy, the son of former Attorney General Robert F. Kennedy and nephew of former President John F. Kennedy, come as his campaign has faltered.
He first entered the 2024 presidential race as a Democrat, but left the party last fall to run as an independent.
He has built an unusually strong third-party base, fueled in part by anti-establishment voters and vaccine skeptics who have followed his anti-vaccine work since the start of the pandemic.
But he has since faced campaign finance problems and mounting legal troubles, including a recent ruling by a New York judge that his name should not appear on the state ballot because he listed a “fictitious” address on his nominating petitions.
Recent polls show his support in the mid-single digits. And it's unclear whether he'll even get that in the general election, since third-party candidates often fail to live up to their early poll numbers when voters actually cast their ballots.
For Mr Trump, Friday will mark the end of a week of contentious state visits in which he sought to distract from Democrats' celebration of Ms Harris's presidential nomination in Chicago.
He visited Pennsylvania, Michigan, North Carolina and the U.S.-Mexico border in Arizona to attend events highlighting his policy proposals on the economy, crime and security, and national security and borders.
It will end the week on Friday with stops in Las Vegas and Glendale.