The one-time journalist and mayor of Gunnedah threw his hat into the ring to represent the Nationals for the seat of Northern Tablelands.

He easily won pre-selection, defeating rivals Claire Coulton and Jock Laurie on a ticket of road funding, law and order, healthcare and education.

The party had earlier selected the independent Mr Torbay as their candidate for the federal seat of New England, before later referring him to ICAC.

It gave Mr Marshall his opportunity to enter state politics, only to find himself referred to ICAC by former mayor of Inverell and NSW Farmers president Mal Peters, who refused to divulge his allegations.

At the time, Mr Marshall said: "I have challenged him [Mr Peters] to put his allegations on the public record and he has not. You cannot take anything this man has to say seriously."

In spite of that, Mr Marshall went on to victory in the by-election with 63 per cent of the vote, easily winning against former Armidale mayors Jim Maher, Herman Beyersdorf, Armidale councillor Dora Koops and Christian Democrats Silvana Nero.

Over time he was to increase that margin to a massive 83 per cent of the Northern Tablelands vote.

One of Mr Marshall's first actions as an MP was to chair a parliamentary inquiry into puppy farms. It made a number of recommendations, however, stopped short of recommending the so-called farms be shut down.

Mr Marshall was in the national spotlight in 2014 for a drink driving offence that followed 17 counts of speeding.

He said at the time he publicly accepted the consequences of his actions and the electorate would not suffer as a result.

Nevertheless, he was forced to surrender two of his ministerial roles, as temporary speaker of the Legislative Council and deputy chair of the State and Regional Development Committee.

But it did little to stop a distinguished, 10-year career in Macquarie Street.

In 2016, then NSW premier Mike Baird appointed Mr Marshall parliamentary secretary for Northern NSW and renewable energy.

He was later promoted to minister for tourism and major events, and the assistant minister for skills in 2017.

Two years later Mr Marshall became minister for agriculture and minister for Western NSW - roles he lost in a cabinet reshuffle in December 2021.

"That's politics. Naturally I'm disappointed, but I look back with pride and have no regrets," he said at the time.

Mr Marshall did not take his eye off the ball in representing local issues, too.

In his time as MP, he oversaw the $60 million upgrade of Armidale Hospital, $80 million redevelopment of Moree Hospital, $30 million redevelopment of Glen Innes Hospital and the completion of a $60 million upgrade of Inverell Hospital.

He ensured protection of the 164-year-old former Armidale Court House, by ensuring the site's inclusion on the NSW State Heritage Register and transferring its ownership to Armidale Regional Council for a nominal fee of $1.

Mr Marshall then went on to secure $925,000 state funding to restore the historic Uralla Court House.

Most recently, Mr Marshall has taken up calls for a parliamentary inquiry into crime in rural and regional NSW, following a crime wave in Inverell.

Just yesterday, April 3, his calls were partly met when NSW Premier Chris Minns launched Project Pathfinder in Moree, a partnership between the NSW Police, NRL and Youth Justice NSW, to provide help for 'at risk' youths.

It is perhaps these achievements that saw Mr Marshall win four straight elections as Nationals MP for the Northern Tablelands.

In the 2023 election Mr Marshall was up against a record field, with 10 candidates nominating, including candidates from several minor parties and two independents.

He trounced the field, gaining an unprecedented 83.3 per cent of the vote.

When he hands in his resignation as Member for Northern Tablelands on May 13, Mr Marshall would have served the electorate for close to 11 years.

"This is not a decision I have made lightly, but it's one I'm now very comfortable with," Mr Marshall said.

"Put simply, I feel it's time for me to move on and take up new challenges."

Within hours of announcing his resignation from politics, tributes were pouring in for Mr Marshall.

Nationals colleague Mark Coulton, who announced his own resignation from politics on March 25, said: "Adam has always been a fierce advocate for the communities in his electorate and has fought hard to secure an enormous amount of funding for the region.

"I've enjoyed working with him on various projects over the years and know he will be missed by his constituents."

Mr Marshall said post politics he intended pursuing opportunities in the corporate world and in his own personal life.

A by-election will be called for the vacant seat of New England later this year.