US presidential candidate Donald Trump falsely accused election rival Kamala Harris of being an anti-Semite who plans to allow the murder of newborn babies, in a speech meant to rally religious supporters Friday that quickly went off the rails.

The vice president, who is married to a Jewish man, has gained ground on Trump in polling since she replaced Joe Biden on the top of the Democratic ticket just days ago.

Former Republican president Trump dedicated much of his address at a religious convention in southern Florida to assailing Harris’s record as a senator and as Biden’s number two, but many of his attacks were smears untethered to reality.

Explaining why 59-year-old Harris had skipped Israeli Prime Minister Benjamin Netanyau’s speech to the US Congress on Wednesday to instead honour a prior commitment, Trump accused her, baselessly, of anti-Semitism.

“She doesn’t like Jewish people. She doesn’t like Israel. That’s the way it is, and that’s the way it’s always going to be. She’s not going to change,” he said.

The remark — coupled with his claim that Harris “is totally against the Jewish people” in North Carolina on Wednesday — marked an escalation in Trump’s incendiary rhetoric, days after his campaign said an attempt on his life had given him a focus on unity.

The hour-long Friday speech, hosted by hard-right Turning Point Action, raised legitimate questions over Harris’s previous statements on policing, immigration and the environment that placed her to the left of current Biden administration policy.

But it was marked by hyperbole and falsehood.

‘Execute the baby’

Trump — a convicted felon who is fighting multiple further indictments — suggested baselessly that the Justice Department and FBI were “rounding up” Christians and anti-abortion activists and throwing them in jail for their “religious beliefs.”

He also called Biden’s decision to exit the election campaign a “coup” by Democrats and said America was a “laughing stock.”

But he saved his darkest vitriol for Harris, calling her a “bum” and a failed vice president who had rejected federal judges for being Catholic and would appoint “hardcore Marxists” to the Supreme Court.

He also accused her falsely of wanting to force doctors to give chemical castration drugs to children and suggested she might cheat to win in November.

“If Kamala Harris has her way, they will have a federal law for abortion, to rip the baby out of the womb in the eighth, ninth month and even after birth — execute the baby after birth,” he claimed, in perhaps his most egregious calumny.

78-year-old Trump, now the oldest major-party nominee in history, is scrambling to reorient an election against someone two decades his junior, having expected to face an 81-year-old incumbent Biden beset by concerns over infirmity.

Just last week, the former reality TV star was in cruise control as he accepted a hero’s welcome — and the official presidential nomination — at the Republican convention in Milwaukee.

Crowning glory

His crowning glory came a week after a gunman nearly killed him at a rally in Butler, Pennsylvania — an extraordinary incident that Trump vowed Friday to commemorate with “a big and beautiful” new rally in the town, although he did not give a date.

Seeking to become the first female president in US history, Harris is tasked with rapidly assembling a campaign against an opponent who has been in near permanent reelection mode since he became president in 2016.

Trump’s predecessor Barack Obama pledged support for Harris earlier Friday, as polls showed her closing the gap that Trump had built over Biden to make the race a statistical tie.

A top California prosecutor and senator before being elected the country’s first female and first Black and South Asian vice president, Harris has highlighted Trump’s criminal conviction and what she said Thursday is a Republican attack on “hard-fought freedoms” in US society.

Democrats leapt on a Trump campaign announcement late Thursday that cast into doubt whether he will debate Harris.

“It shows that he’s afraid,” Transport Secretary Pete Buttigieg, a major Harris campaign advocate, told MSNBC.

“It shows that he knows that if the two of them are on a stage together, it’s not going to end well for him.”