A bid to unseat Sinn Féin MP Ms Michelle Gildernew will be heard at Belfast High Court on Monday.
Ulster Unionist Party chairman Mr James Cooper alleges that "actions and threats" resulted in Ms Gildernew, rather than himself, winning the Fermanagh-South Tyrone seat.
Both parties dispute events at a polling station in the border village of Garrison, Co Fermanagh, during the Westminster election on June 7th.
Mr Cooper, who received just 53 votes less than Ms Gildernew, maintains the polling station at St Martin's school remained open after the poll had officially closed.
"The number of votes issued at Garrison after 10 p.m. could have affected the outcome of the election," he said.
Mr Cooper alleged a large number of Sinn Féin members "invaded" the polling station.
The court will hear "how that situation was handled by the presiding officer and how he dealt with the intimidation that took place," he said.
Mr Cooper said he hoped the court would declare the election result void and order a by-election.
Ms Gildernew has dismissed the allegations as "completely spurious". The station did reopen after 10 p.m., she said, "but only for 10 minutes during which time only seven or eight ballots were cast".
"The station had opened 10 minutes late in the morning and in the interests of balance the presiding officer decided to reopen".
Ms Gildernew denied any intimidation had taken place and said RUC officers in the village had not been asked to intervene.
The case is expected to last up to three days and will be heard by two judges.