Long-time Ontario MP Pierre Poilievre announced today he will not run for the Conservative Party leadership, saying it would be too tough on his family at this time.

Poilievre was expected to announce his candidacy on Sunday in Ottawa, but in a Facebook post late Thursday he said he would not be joining the race to replace outgoing leader Andrew Scheer.

"Over the last several weeks, I have been building a team and support for a possible run for the Conservative leadership. In criss-crossing the country, I have been overwhelmed with the favourable response," he wrote on Facebook.

"I knew it would be hard on my family life to do this. But I did not realize how hard. It is harder still because I had just spent the earlier 18 months campaigning furiously to win back my seat in the recent federal election, during which I mostly missed the first year of our baby's life."

"As such, my heart is not fully engaged in this leadership race. Without being all in, I cannot be in at all. So I have decided not to seek the leadership of the party at this time."

Poilievre said he will continue to serve his Carleton constituents as an MP.

He said he is not currently supporting any other candidate, but will look for a "strong fiscal conservative who will unleash free enterprise so people can achieve their dreams through hard work."

WATCH | Ontario MP Pierre Poilievre won't run for the Conservative leadership:

Perceived as a front-runner for the Conservative leadership, Pierre Poilievre announced he won’t enter the race. 1:57

As recently as this week, Poilievre was outlining policy positions in a manner that suggested he was determined to run.

He told the Toronto Star that under his leadership, Conservative MPs would be free to bring forward legislation on abortion and vote according to their conscience, but that such legislation would not be adopted under a Conservative government under his leadership.

He also lashed out at Richard Décarie, a social conservative who says he intends to join the leadership race, for comments he'd made on CTV's Power Play suggesting that being gay is a "choice".

"The comments are as unacceptable as they are ignorant. You do not speak for Conservatives — or for Canadians. Being gay is NOT a choice. Being ignorant is," Poilievre wrote on Twitter.

The comments are as unacceptable as they are ignorant. You do not speak for Conservatives—or for Canadians. Being gay is NOT a choice. Being ignorant is. <a href="https://t.co/7zWLwQbQOH">https://t.co/7zWLwQbQOH</a> —@PierrePoilievre

Poilievre's wife Anaida also posted about his decision on Facebook, saying it was not taken lightly.

"Our family is young. My husband just wrapped up one full year of campaigning every day ... thus missing most of our daughter's first year of life. We can't have him missing more. Time cannot be bought back, and our baby girl is growing way too fast," she wrote.

Challenge 'bigger than expected'

"While we felt ready to tackle this challenge together as family, logistically it became a challenge bigger than expected," she added. "We wish to be together more, and I hope people can understand that."

Former Conservative cabinet minister Peter MacKay has announced on Twitter that he intends to join the race. He's expected to formally join the race Saturday.

Ontario MP Marilyn Gladu also has said she intends to join the race, and Ontario MP Erin O'Toole is expected to be a candidate.

O'Toole's deputy campaign manager Melanie Paradis said Poilievre's decision to opt out means a narrow field of serious candidates.

"It's now a two-way race. We need a leader for 2020, not the 90s. A leader who can unite all parts the Conservative movement. That's Erin O'Toole," she said in a statement to CBC.

Pierre has been a champion for our party and the conservative movement. I know he will continue to be an important voice. <a href="https://t.co/ayvlN6XMOV">https://t.co/ayvlN6XMOV</a> —@ErinOTooleMP

Gladu called the effort to frame the race as a two-person contest "offensive."

"Clearly, Erin can't do math," she told CBC, noting that she is a "fully credible candidate."

"He's counting his chickens before they're hatched."

O'Toole responded to Poilievre's announcement on Twitter.

"Pierre has been a champion for our party and the conservative movement. I know he will continue to be an important voice," he wrote.

Gladu told The Canadian Press today that the party's rules on fundraising and networking can be major barriers for women in politics.

The rules require that candidates gather $300,000 in fees and 3,000 signatures in just over two months.

The Conservative caucus is meeting in Ottawa Friday and Saturday to prepare for a return to the House of Commons Monday.