Local solicitor Patrick Conaghan, business owner and electrician Jamie Harrison and Port Macquarie newsagent Chris Genders will front The Nationals' membership during the preselection process.

A spokesperson for the party said all three candidates were outstanding.

"The NSW Nationals’ preselection process is one of the finest examples of democracy in action, as party members get to decide who will represent them in the federal parliament," the spokesperson said.

"Our party undertakes strict vetting procedures to ensure that our candidates are suitable to be elected as members of the federal parliament.

"The Cowper preselection meeting is scheduled to take place on November 3, 2018."

The ALP has already preselected Andrew Woodward as its candidate for the federal poll while the Greens have nominated Dr Sally Townley.

The Nationals extended the date to select a new candidate to replace the retiring long-serving member Luke Hartsuyker.

At the time, a spokesperson for the party denied the extension showed there was a lack of possible candidates.

“The Nationals are busy getting on with the job of delivering for the people of Cowper," the spokesperson said at the time.

But ALP candidate for Cowper Andrew Woodward declared his disbelief about the extension of nomination date, claiming the Nationals were unable to find a suitable candidate.

“It is incredible to think that they can’t find an acceptable candidate for a seat they have held for 97 out of the last 99 years,” he said in a statement issued to the media.

“The outgoing member announced on August 8 2018 that he was departing. Six weeks on, the National Party can’t come up with anyone they’re happy to win. This defies belief.”

Independent candidate at the 2016 election and former federal MP for Lyne, Rob Oakeshott is yet to confirm if he will contest the next election.

The Cowper electorate includes the cities of Port Macquarie and Coffs Harbour with other major centres including Kempsey, Nambucca Heads, Macskville and South West Rocks.

Mr Hartsuyker has served the electorate for 17 years, retaining the seat for the conservatives in 2001 from the then retiring member Gary Nehl.

Mr Hartsuyker topped the poll at the 2016 election and holds the seat with a 4.56 per cent margin on two candidate preferred over Independent candidate Mr Oakeshott.

The seat has been considered conservative since Francis Clarke claimed the seat in the first federal election in 1901 for the Protectionist Party.

Earle Page held the seat for close to 42 years from 1919. He was the caretaker prime minister when he contested the 1939 federal election.

The ALP did hold the seat in 1961 for two years when Frank McGuren snatched the seat from Mr Page, who was gravely ill. Mr Page subsequently passed away 11 days after the election unaware that he had lost the seat.

An election date is yet to be set by prime minister Scott Morrison.