Former DUP leader Peter Robinson has stressed the need for the party to be led from the centre going forward.
Mr Robinson’s comments appear to suggest he favours Jeffrey Donaldson over Edwin Poots in the two-horse race to replace the departing Arlene Foster.
DUP Westminster leader Mr Donaldson would be widely viewed as a more moderate candidate than Stormont Agriculture Minister Mr Poots.
In his regular column for the Belfast News Letter, Mr Robinson also challenged the rationale for the party to shut down any public campaign activity in the contest.
The party is preventing candidates and other DUP politicians from speaking publicly about the race, insisting the leadership should remain an internal matter.
Branding last week’s internal heave against Mrs Foster as “brutal and publicly humiliating”, her predecessor as Stormont first minister also warned against underhand tactics in the campaign, expressing concern at some of what he has witnessed so far.
Mr Robinson wrote: “The DUP will not be the largest political party if it sheds elements of its support base.
“There is no viable alternative unionist party capable of gathering support from a wide cross-section of the public.
“The DUP from the latter stages of Ian Paisley’s leadership broadened its base and with it the party’s appeal. This necessitates leading the party from the centre of unionism and not its extremes.
“Move to the edges and you lop off an important portion of people at the other end of the party spectrum. This is the route to minority status. It’s not rocket science.
“If the principle of leading from the centre is important for gaining and keeping party support, it is even more critical for maintaining support for the Union.
“The retention of the Union is entirely dependent on the widest and broadest level of support – well beyond, but including, those who support what detractors call the hardcore old-DUP message.
“Nobody should conflate a central unionist stance with a soft unionist stance.
“When Ian Paisley led the DUP to becoming the largest party it was not on the basis of being soft.”
The race will be decided by a small electorate of 36, comprising the party’s 28 MLAs and eight MPs.
Mr Robinson said there is a need to address a wider audience ahead of the vote next Friday.
“No-one should be surprised if the wider unionist family feel they have skin in the game and while it is impossible to widen out the electoral college, it is incumbent on the candidates to publicly address this wider audience and convince those they will later rely on for support that they are worthy of their trust,” he said.
On the conduct of the campaign, the ex-DUP leader said: “What would be highly dangerous would be the insertion of peaky blinders manoeuvres into a party contest.
“Organised third-party social media attacks, negative briefings and fake information should have no part of a contest between colleagues. There are sadly early signs of the deployment of such tactics.
“While it was no real shock that there were members who felt it was time to see new leadership, the brutal and publicly humiliating manner of Arlene’s dismissal will, on its own, have created difficulties for a new leader trying to unify the party.
“Yet, the debris left on the landscape if the campaign is conducted using guerrilla attacks will potentially cause irreparable damage. So real caution is needed.
“If not handled properly, differing opinion can lead to division and division can lead to a split. Unionism cannot afford that and may not recover from it.”
While Mr Poots and Mr Donaldson are vying for the leadership, three candidates are running for the post of deputy leader.
MP Gregory Campbell and MLAs Paul Frew and Paula Bradley are competing to replace the outgoing Lord Dodds.