EXETER (New Hampshire) • Former United States president Bill Clinton has hit the campaign trail in support of his wife Hillary's bid for the White House, touting her record in public office and dodging discussion of his own.

Mr Clinton's step back into the limelight on Monday was his first solo campaign appearance for his wife. He called her the most qualified presidential candidate in decades.

Speaking to a crowd of supporters in the early-voting state of New Hampshire at a town hall in Exeter, Mr Clinton said: "I think she's proved she knows how to get things done... Everywhere she went, she made something good happen."

Monday's stops were the first of what are expected to be many that Mr Clinton, 69, will make, with just four weeks until the first votes are cast in the nominating process for the November election.

His late introduction to the campaign trail could be a strategically significant move for the former secretary of state, who still trails Vermont senator Bernie Sanders in New Hampshire opinion polls.

But while Mr Clinton's lasting popularity among Democrats makes his support a sterling endorsement for any candidate, scrutiny of his past infidelities raised by Republican pack leader Donald Trump has reintroduced a sore point in his legacy to voters too young to remember the scandal.

In the 1990s, Mr Clinton, while still in office, admitted to a sexual relationship with a White House intern. Mr Trump has sought to exploit the scandal, calling the former president "fair game".

He stepped up his personal attacks on the Clintons on Monday, criticising Mrs Clinton for calling him sexist. "How can she do that when she's got one of the great women abusers of all time sitting in her house, waiting for her to come home for dinner," he told CNN.

"The worst thing Hillary could do is have her husband campaign for her. Just watch," he tweeted to his 5.5 million followers on Sunday.

On Sunday, Mrs Clinton was heckled by a Republican state representative in New Hampshire over her husband's sex scandals. "You are very rude," she snapped back.

Mr Clinton shied away from addressing the controversy directly during his speeches, but in a thinly veiled criticism of Mr Trump, he bashed Republicans for attempting to make a caricature of his wife's career. "She's got the proven ability to get the best out of a difficult situation," he said to volunteers in Dover. "At a time when we have been driven apart by the communities of collective resentment, she has never stepped into a room where she didn't make something good."

At a rally at a community college in the city of Nashua, Mr Clinton did not mention Mr Trump in a 30-minute speech, but paid tribute to his wife's determination to make America a fairer, safer country for the poor and struggling middle classes. "I do not believe in my lifetime anybody has run for this job in a moment of great importance who is better qualified by knowledge, experience and temperament to do what needs to be done," he said.

He also warned that key gains in environmental and healthcare policy would be reversed if the country elects a Republican president.

Calling himself a "happy grandfather", a relaxed Mr Clinton said he thought Mrs Clinton was "the most amazing person" when they met and fell in love 45 years ago at Yale Law School. She could have won any job, but wanted only to provide legal aid to the poor, said her husband. "Everything she touched, she made better," he said.

"In an uncertain world, where borders look more like nets than walls, and no one is in total control, she understands what it takes to keep our country as safe as possible," he said.

Mrs Clinton leads national polls for the Democrats ahead of New Hampshire's vote on Feb 9, the nation's first presidential primary.

REUTERS, AGENCE FRANCE-PRESSE