Donald Trump’s youngest son Barron attended his first campaign rally where he was met with rapturous applause by his father’s supporters.

Barron, who recently turned 18, pumped his fists and waved at the crowd as the elder Trump said: “Welcome to the scene, Barron.”

Reacting to the crowd’s applause, Mr Trump said that Barron “might be more popular than Don and Eric”, Donald Trump’s two older sons.

“He had such a nice easy life, now it’s a little bit changed,” Mr Trump added.

Barron, who stands at 6ft 7in tall, had been shielded from the limelight throughout his childhood but is understood to be preparing to take a more active political role.

The Republican Party named the 18-year-old as a delegate in next week’s Republican National Convention, but he declined, citing other commitments.

It came after Melania Trump, Barron’s mother, on Monday night raised $1.4 million for her husband’s campaign at a fundraiser in the couple’s Trump Tower penthouse in New York City.

The fundraiser was for Log Cabin Republicans, a Republican-affiliated LGBT rights group, who described the event as “amazingly spectacular”.

Ms Trump reportedly “stunned all in attendance” with a “fire engine red Valentino dress”, an attendee was quoted as saying.

There had been speculation that Trump would use Tuesday’s rally at a Florida golf club to announce his running mate for November’s presidential election.

Trump teased Marco Rubio, the senior senator from Florida, as his potential selection throughout his speech but did not anoint him.

Instead Trump used the event to escalate attacks on Joe Biden and Kamala Harris, his vice president.

“Joe’s own party wants him to throw in the towel and surrender the presidency after a single 90-minute performance,” Trump said, referring to Mr Biden’s “disastrous” first US presidential debate last month which prompted major Democrat party donors to urge the 81-year-old US president to step aside.

He also challenged the president to a charity golf match after disputing Mr Biden’s ‘handicap’ during the June 27 debate.

Turning to Ms Harris, who is considered a leading candidate to succeed Mr Biden should he step down, Trump said: “If Joe had picked someone even halfway competent as his No. 2, they would have bounced him from office years ago.”