The byelection hasn't been called yet, but the campaign to fill the late Jim Flaherty's House of Commons seat is about to become a two-woman race.

On Thursday night, local New Democrats are expected to formally endorse riding president Trish McAuliffe as the party's candidate in the still undeclared byelection in WhitbyOshawa.

Earlier this month, Whitby businesswoman Celina Caesar-Chavannes was acclaimed as the Liberal candidate-in-waiting.

McAuliffe, a community organizer and social activist, ran against Flaherty in 2011. She topped Liberal contender Trevor Bardens to come in second, albeit garnering fewer than half the votes as the former finance minister, who won the riding with 58 per cent support.

Celina Caesar-Chavannes  - Liberal byelection candidate in Whitby - Oshawa

Celina Caesar-Chavannes was acclaimed as Liberal candidate in the still-undeclared byelection earlier this month. (Facebook)

According to the meeting notice posted to McAuliffe's Facebook page, Scarborough-Rouge River New Democrat MP Rathika Sitsabaiesan will speak at the event, which will be held at a local community centre.

"I know we will bring plenty of energy into the room," she predicted.

In an earlier entry announcing her candidacy for the race, McAuliffe noted that late leader Jack Layton "continues to be my inspiration."

"I know he will be guiding my hopes and my fears along the way," she added.

Conservative spokesman Cory Hann declined to provide an update on the status of his party's nomination process. 

"Members in Whitby - Oshawa will be notified when the nomination opens for the riding," he told CBC News by email.

Under parliamentary rules, the byelection must be called by Oct. 25, although the law doesn't set a deadline on when the vote must be held.