Nova Scotia MP Robert Chisholm has dropped out of the NDP leadership race.
He made the announcement Wednesday on Twitter, and posted a longer explanation on his website.
"As I said when I started this campaign, it is my desire to do what I think is best for my constituents, for the New Democratic Party and for Canada," Chisholm wrote.
"That has always guided my decisions. It is under the same guiding principles that today I am ending my campaign to become the next leader of the New Democratic Party of Canada."
Chisholm was the only unilingual candidate in the contest and struggled during the French portions of the leadership debates.
He cited his lack of French as one reason for dropping out of the race.
"While many agreed that our next leader needs real experience and a strong vision, many also spoke about the need for the next leader to speak fluent French, right from day one," Chisholm wrote.
"I've determined that, for the majority of party members, this is a non-negotiable qualification. Although I am working hard on my French — and will continue to do so — I will not meet this threshold by March 24th."
Eight candidates remain in the running to replace the late Jack Layton: Niki Ashton, Nathan Cullen, Paul Dewar, Thomas Mulcair, Peggy Nash, Romeo Saganash, Martin Singh and Brian Topp.
A spokesman for Chisholm said he isn't endorsing any candidate at this time.
New Democrats will pick a new leader in March. Nycole Turmel has served as interim leader since Layton died in August.
The next NDP leader takes over a party that jumped from having a few dozen MPs to more than 100 after the spring federal election.
For the first time in its history, the party is the official Opposition in Ottawa.
"We must strive to unite and to grow our party," Chisholm wrote.
"We must continue to show Canadians we deserve to be the official Opposition and that we take the responsibility seriously. And we must include and engage all Canadians."
Chisholm, a former Nova Scotia NDP leader and now MP for Dartmouth-Cole Harbour, is well known in the province for leading his party to a breakthrough to Opposition status in the 1998 provincial election, taking 19 of the 52 seats in the legislature.
After leaving provincial politics in 2003, he worked as a researcher and regional director of CUPE for four years.
He was co-chair of the Nova Scotia NDP government's transition team when the party took office in June 2009.