On the first night of the Republican Party convention, the president's eldest son, Donald Trump Jr, took centre stage and commanded the nation's attention.

"Trump's policies have been like rocket fuel to the economy," Mr Trump said during his speech, praising his father's leadership. But his most powerful lines were not about his the president; they were swipes at Joe Biden, the Democratic nominee for the presidency.

"Biden's radical left-wing policies would stop our economic recovery cold," Mr Trump said. He warned conservatives that Democrats would undo the economic gains that people had made with his father in the White House.

"Biden has promised to take that money back out of your pocket and keep it in the Swamp," Mr Trump said, adding: "That makes sense, considering Joe Biden is basically the Loch Ness Monster of the Swamp. For the past half-century, he's been lurking around in there."

A fierce advocate for his father's platform, Donald Trump Jr's supporters say he can electrify a room while his detractors accuse him of pouring petrol on the flames.

His presentations are laced with full-throated attacks on liberals, Hunter Biden - Joe Biden's son - and on the media (that's when the crowd roars).

Firebrand speaker, sportsman and big-game hunter, Mr Trump is doing everything he can to help his father win re-election. The Republican strategy has focused on energising the president's base of supporters, and they see the younger Mr Trump as their ace in the hole.

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He has an unusual rapport with the president's supporters, many of whom live in rural parts of the country and also love to hunt. "He's viewed as a conduit to the Trump base," explains Ron Bonjean, a Republican strategist with ties to the White House.

They like his "no-nonsense" style, says Michael Kuckelman, the chair of the Kansas Republican Party who is now at the Charlotte convention.

Many of the president's base like the way that the younger Mr Trump has at times gone even further than his father, supporting, for example, the gun industry's efforts to have restrictions on silencers eliminated.

He is also admired for his boldness - he has aligned himself with colourful characters. Last year, he appeared at a rally for We Build the Wall, a group that was founded as a way to raise funds for the wall.

Founders of the group have recently been charged with defrauding donors.

In his role as a campaign speaker, Mr Trump is often surrounded by signs emblazoned with his father's name. In these moments, his part seems preordained: when you have the same name as your father, it is natural to slip into the role of cheerleader. And while some men might chafe at the part, he has thrived in his father's shadow.

He is treated like a rock star at conservative venues.

Lawrence Levy, the executive dean of Hofstra University's National Center for Suburban Studies, says that Mr Trump is an unusually effective advocate for his father on the campaign trail. And it could be a stepping stone to a more prominent role.

"The successful sons of powerful people learn not just to live but to thrive in what may seem like their father's shadow but will someday disappear and they will be the family's patriarch," says Mr Levy.

BBC