In the final weeks of his campaign for re-election in 2012, Barack Obama joked during a visit to St Petersburg, a coastal city in central Florida, that he should appoint Bill Clinton to a new post: "Secretary of Explaining Stuff." As Obama stumbled in the early stages of that campaign, Clinton emerged one of his most effective advocates, earning praise for his steadfast defence of Obama's domestic agenda and his persuasive case for giving his successor four more years in the White House.

Four years on, it’s the former president who has turned up in St Petersburg in the closing stages of an election campaign, this time to make the case for his wife Hillary. Some things don’t change: Bill Clinton is still in his element when he is explaining stuff.

In a 40-minute speech to a crowd of several hundred supporters in a basketball arena in Wildwood in south "St Pete", a poor district with a large proportion of African-Americans, Clinton delivers a forceful defence of Hillary's economic plans and warns of the dangers facing low-income families under a Trump White House.

With so many working-class whites having already been drawn to the Republican nominee and early voting figures showing lower turnout so far among African-Americans compared with 2012, Clinton’s task is to mobilise Democratic voters to ensure Hillary can win Florida, the biggest swing state and a key target for the Trump campaign. “If people who are for Hillary vote for Hillary, she’ll win Florida and be our next president,” Clinton says to roars of approval.

Loud crescendo

Now aged 70, Clinton is thinner, more wizened and more gravelly-voiced than he was, but neither his natural charm nor his fondness for policy detail have dimmed. Microphone in hand and speaking without notes, he paces up and down the stage, starting off quietly and building up, over the course of a speech that blends policy ideas with folksy homespun anecdotes, to a loud crescendo that has the crowd cheering wildly.

“We need to get this country back in the future business,” he says, contrasting his wife’s vision of a fair, competitive and optimistic country to what he portrays as the dystopian worldview of “her opponent”, as Clinton calls Trump throughout. It’s a message tailored to the crowd, emphasising Hillary’s plans to improve access to college through a new loan scheme, help the weakest in society and those with disabilities and encourage small business-owners. At one point, Clinton appears on the verge of tears as he recalls a letter Hillary received from a 13-year-old disabled boy pledging his support.

"I thought he was a good president," says Betsy Larson, an IT manager who has come to hear Clinton speak. For her, Clinton is a reminder of a time when America was doing better. "He was a centrist, did well with the economy and worked across the aisle, which is what we're sorely missing the last many years."

Another local man at the rally, business-owner David Benedict, admits he is a Trump voter but came along this evening because his Lithuanian wife Ausra really wanted to see Clinton. He won't change his mind ("Donald Trump has always been an idol for me") but he is impressed by Clinton's performance. "He's a rock star. He's a superstar. He's a very good talker. I already knew that, but when you go to an event you see the energy of the crowd and the energy he creates," Benedict remarks.

In his stump speech, Clinton ridicules Trump’s signature campaign slogan, Make America Great Again, dismissing the idea that the US should return to an imagined halcyon past. “Fifty years ago, this wasn’t such a great country for African-Americans, for immigrants, for religious minorities,” he says. Under a President Trump, “we’re gonna have just what we had 50 years ago, just not economically”.

Low-key role

A midweek evening event in the basketball court at the Thomas Jackson Recreational Centre, with its capacity of just a few hundred, is a far cry from the huge venues where some of Hillary Clinton's other surrogates, such as the Obamas, Bernie Sanders and Joe Biden, have been addressing crowds in recent weeks. This has been a pattern of the campaign, with Bill deployed in a more low-key role – "my little bus tours", he joked last month – that focuses on smaller and more remote locations, usually with large contingents of working-class whites and African-Americans, two vital groups with whom the former president has always had a strong rapport.

But other factors may also lie behind the modesty of Bill Clinton’s public role in the campaign. While his favourability ratings remain strong (49 per cent, according to Gallup, compared with 52 per cent for Barack Obama), Trump’s attempts to put the former president’s infidelity and alleged sexual misconduct front and centre of the campaign is further reason for the Clinton camp to keep him out of sight, lest his prominence keep the stories on the news agenda.

Moreover, some of the themes of his presidency, such as free trade and welfare reform, are less popular in Democratic heartlands in 2016 than they were in 1996. Bill’s freewheeling stump speeches sound fresh and vigorous, but his style has left him prone to moments of ill-discipline, as when he described Obamacare as “the craziest thing in the world”.

Whether Bill would remain quite as discreet in a Hillary White House is another matter. "Two for the price of one" – a line he used when running for office in the 1990s – is no longer heard, but speculation has centred on whether he could play a role in brokering Middle East peace talks or act as a liaison point on Ireland.

Opponents rounded on Hillary earlier this year when she suggested Bill would be “in charge of revitalising the economy”, and since then the couple have largely steered clear of the topic.

Betsy Larson believes Bill has an important role to play. Listening to him speak reminds her how natural a politician he always was. “I think she’s way smarter than he is, but I don’t think she relates as well to people. But I think she has always been a really good student, and that’s one of the reasons I think she’ll be a good president.”