OTTAWA -- The Conservative Party’s outgoing deputy leader has put her support behind leadership candidate Peter MacKay, just hours after announcing her resignation from the position.

Leona Alleslev made the announcement on Twitter on Monday morning, as the party's four leadership candidates look to shore up last-minute support before the August 21 deadline for mail-in ballots.

"Canada faces an uncertain future. Canada needs a leader who has the experience and a plan to tackle the priorities of our time. That is why Peter MacKay has my support," reads the tweet.

On Sunday evening, Alleslev made her decision to step down as deputy party leader public, citing a need to engage in the final weeks of the campaign.

"The selection of the next leader of the Conservative Party of Canada is too important a decision for me to stand to the side. Today, I am stepping down as Deputy Leader of her Majesty’s Loyal Opposition to engage more actively in the leadership campaign," the tweet reads.

Alleslev was appointed deputy leader by Andrew Scheer in November, 2019, about a year after causing a stir in the House of Commons when she crossed the floor, swapping her Liberal badge for a Tory one.

"I stand here today deeply concerned for the future of our country. After three years of hope and hard work, I find myself asking: Am I doing everything I can to serve the citizens of Aurora—Oak Ridges—Richmond Hill and my country?," Alleslev said when delivering her announcement in the House in September, 2018.

"My attempts to raise my concerns with the government were met with silence. It is my duty to stand and be counted. Our country is at risk."

The Ontario MP quickly adapted to her role under the opposition tent, grilling her former colleagues for their foreign affairs policy and most recently for their pandemic response.

She was steadfast in her loyalty to Scheer and defended his positioning on social conservative issues during the fall federal election campaign.

In an interview on CTV’s Question Period shortly after she became deputy leader, she questioned the allegiance of Scheer critics who railed against the leader for his campaign performance and shed doubt on his ability to lead following the party’s devastating loss.

"I think that there are certain obviously disgruntled people and I'm very disappointed in them, because if they really cared about the country and they really cared about the conservative movement, they would wait for the external review that we are investing in, to find out exactly where we can do better and what we did wrong," Alleslev said at the time.

In her resignation letter Sunday, she celebrated her party’s recent accomplishments and expressed her commitment to help build a strong Tory base.

"Together, our Conservative team has held the government to account and challenged them to address critical policy flaws that they had failed to consider or deliberately neglected," reads the letter.

"Canada faces an uncertain future. The Conservative Party of Canada is in the process of choosing a new leader that will guide us through the nation’s next chapter."

Peter MacKay, Erin O’Toole, Leslyn Lewis and Derek Sloan are vying to replace Scheer from the party’s top post. MacKay, a former cabinet minister, and O’Toole, a sitting MP, are widely considered to be the front-runners.

Alleslev represents a part of the old riding that once belonged to MacKay’s former partner and Conservative turned Liberal MP Belinda Stronach.