The widow of conservative activist Charlie Kirk has said the Turning Point USA organisation he founded will help elect JD Vance as president in 2028, despite the current US vice-president having yet to announce he is running.

Erika Kirk's endorsement on Thursday came on the opening day of Turning Point's annual America Fest conference, the organisation's largest gathering since her husband was shot dead in September.

We are going to get my husband's friend, JD Vance, elected for 48 in the most resounding way possible, Kirk said, referring to the 48th president. Trump is the 47th.

Vance, meanwhile, is scheduled to speak at the event on Sunday.

Turning Point has been credited with helping Republican President Donald Trump expand his coalition of support, leading to his 2024 presidential election victory.

Her announcement ahead of Trump's one-year mark in office signals early jockeying to be his successor ahead of the 2028 election.

After Kirk gave her opening remarks, the stage at the Phoenix Convention Center in Arizona turned into a political mudslinging contest as tensions within the conservative movement were laid bare.

Podcaster Ben Shapiro lobbed attacks at media rivals Candace Owens, Tucker Carlson, Megyn Kelly and Steve Bannon, calling them fraudsters and grifters.

The people who refused to condemn Candace's truly vicious attacks - and some of them are speaking here tonight - are guilty of cowardice, Shapiro said.

Owens, a former Turning Point employee who hosts a popular podcast, has been a thorn in Republicans' side and pushed various conspiracy theories, including baseless suggestions about Charlie Kirk's murder.

It comes at a time when there has been growing speculation about Trump's hold on the Republican party and infighting among factions of the president's supporters about the future of the MAGA movement.

Shapiro also criticised former Fox News host Carlson for interviewing Nick Fuentes, a far-right political commentator and Holocaust denier, on his podcast in late October, drawing widespread condemnation.

After Shapiro, Carlson took the stage and shot back at Shapiro.

That guy is pompous, Carlson said. Calls to deplatform at a Charlie Kirk event? That's hilarious.

Charlie Kirk's Turning Point events were known for addressing controversial and divisive topics. Supporters saw it as necessary for free speech. Critics saw it as hate-mongering.

Authorities said Charlie Kirk's alleged assassin - Tyler Robinson - told his romantic partner that he killed Kirk because he had enough of his hatred.

Erika Kirk told the Turning Point conference: You won't agree with everyone on this stage this weekend. And that's okay. Welcome to America.

Since the assassination, she said, we've seen fractures, we've seen bridges being burned that shouldn't be burnt.

Trump has recently encountered a series of setbacks within his Republican party, including a public falling out with his former ally Marjorie Taylor Greene and the impending release of the Epstein files, which a majority of Republicans voted for despite Trump's initial discouragement.

The four-day America Fest conference was scheduled to continue through the weekend, with Vance and Donald Trump Jr scheduled as guest speakers on Sunday.