Ulster Unionist leader David Trimble is confident that he will fend off the challenge to his leadership in Saturday's ballot.
However a close contest could encourage further infighting about the course of the peace process.
The Rev. Martin Smyth, who is standing against Timble, a Nobel Peace Prize laureate, says the key issue is the disarmament of the Irish Republican Army.
The British government suspended Northern Ireland's flegling Protestant-Catholic administration in February to prevent Trimble from leading an Ulster Unionist walkout over the IRA's refusal to begin disposing of its weaponry.
Smyth has said he would not take the party back into the administration unless the IRA first starts disarming. There should be "no guns outside the door, no guns under the table, no guns on the table," he declared.
Trimble has indicated more flexibility, saying in Washington earlier this month that the government could be restored if the IRA issued a firm pledge to disarm.
Six of the party's 10 members of the British Parliament are backing Smyth.
The leadership vote, however, will be taken by up to 858 delegates from constituency associations, who in the past have backed Trimble.
The contest reflects the divisions that have beset the Ulster Unionists throughout the peace process.
Smyth, a former leader of the hard-line fraternal Orange Order, opposed the peace agreement concluded on Good Friday 1998, but now says he does not object to sharing power with Catholics in a new regional government.
Trimble, once considered a hard-liner, has moved his party in new directions since winning the leadership in 1995 - in a five-man contest in which Smyth finished last.
Trimble endorsed the Good Friday accoant vote in an Ireland-wide referendum. Then, after demanding IRA disarmament as the price of forming the new Cabinet, he decided last year to enter the administration with nothing more than a promise that disarmament would follow.
In November, 42 per cent of the Ulster Unionist Council voted against Trimble's decision to enter the administration. Saturday's vote will provide some indication whether opposition to Trimble's policies has increased or decreased since then.
A close win would decrease Trimble's room for maneuvering on the arms issue.
On the eve of the vote,Trimble called the leadership challenge a "distraction" from the battle to force the IRA to honour its obligation to disarm if the Ulster Unionists are to sit in the Cabinet alongside members of IRA-allied Sinn Fein party.
"Part of what I was doing in Washington was calling on republicans to come back to the table and put back more on the table than what was on it in the past," he said.Reuse content