With one viral line on cable TV – “these guys are just weird” – Tim Walz vaulted into contention for the job of Kamala Harris’s running mate.

The 60-year-old brings with him a folksy, plain-spoken and sharp-tongued approach to the Republican opposition.

He also comes with a compelling resume – a public school teacher, football coach and National Guardsman before he entered politics.

His political experience, representing a Republican-leaning district in Congress and then later passing left-wing policies as Minnesota’s governor, could have broad appeal at a time when American politics is so polarised.

A native of rural Nebraska, Mr Walz farmed and hunted in his summertimes and enlisted in the Army National Guard at 17. He would serve in the volunteer force for 24 years.

His father, a public school administrator, encouraged him to join the military before he died from lung cancer when Mr Walz was 19.

The Minnesota governor has spoken of how Social Security survivor benefits sustained his mother, and how the GI Bill paid for his college education.

Armed with teaching degrees, Mr Walz took on a one-year teaching post in China around the time of the Tiananmen Square massacre.

He later honeymooned in the country with wife Gwen Whipple and also organised summer educational trips to China for US students.

After returning home to Nebraska, Mr Walz became a teacher and American football coach until his wife – another teacher at the school – drew him back to her native Minnesota. They now have two children.

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As a coach at Mankato West High School, Mr Walz helped build up an American football programme that led the school to its first state championship.

He also earned plaudits for agreeing to be the faculty adviser for the school’s gay-straight alliance at a time when homosexuality was largely frowned upon.

He first ran for office in a largely agricultural district that spans across southern Minnesota, which is fairly rural and Republican-leaning.

But Mr Walz campaigned as a moderate who cared about public service and veterans’ advocacy, leading to an election upset.

Over his 12 years in Congress, it was hard to label his ideology.

He voted in favour of the Affordable Care Act, co-sponsored pro-labour measures, including a bill to raise the minimum wage, and backed an unsuccessful cap-and-trade effort for reducing carbon emissions.

But he also found common cause with Republicans.

He voted to continue funding the wars in Iraq and Afghanistan, supported tighter vetting of refugees entering the US, and tried to block the Obama-era bailout of banks and car companies after the 2008 financial crash.

Once endorsed by the pro-gun National Rifle Association (NRA), which donated to his campaign, he spoke out in favour of an assault weapons ban after the Parkland school shooting and lost their backing.

Mr Walz won the 2018 Minnesota governor’s race by more than 11 points but his first term was overshadowed by the Covid pandemic and the killing of George Floyd by a police officer in Minneapolis.

Republicans heavily criticised Mr Walz for being slow to deploy the National Guard even as some protests grew violent.

But the governor won re-election and his second term has overseen a busy period with Democrats controlling the state legislature by a single seat.

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Democrats have enshrined abortion rights, enacted paid family and sick leave, strengthened gun laws, funded universal free school meals and invested in affordable housing.

The frenetic activity caught the eye of former President Barack Obama who wrote: “If you need a reminder that elections have consequences, check out what’s happening in Minnesota.”

Largely unknown on the national scene, Mr Walz has quickly gathered buzz in recent weeks for his acerbic descriptions of Republicans.

“These are weird people on the other side,” he recently told MSNBC, a label that has been widely repeated. “They want to ban books. They want to be in your [doctor’s] exam room.”

But Republicans have been quick to characterise what he has done in Minnesota as too radical for ordinary Americans.

Tom Emmer, the third-highest ranking Republican in the US House of Representatives, accused Mr Walz of trying “to turn Minnesota into Kamala Harris’ home state of California”.

But allies, including labour leaders, believe Mr Walz can broaden Ms Harris’s appeal to rural and working class voters.

Angie Craig, a House Democrat locked in a competitive race for re-election, praised Mr Walz as “a battle-tested leader”.

As “a proven winner who has never lost an election across many tough races”, she told the BBC she believed he would be the best possible addition to the Harris ticket.