Following Stephen Harper's resignation as leader of the Conservative Party of Canada, O'Leary attended Conservative party gatherings in February and May 2016, leading to public speculation about whether he would run for 2017 leadership election.

In February 2016, Maxime Bernier, a Conservative Quebecois politician, criticized O'Leary, calling him a "tourist" for wanting to be prime minister without being able to speak French.
Bernier later explained that he wanted all leadership candidates to learn French and praised his fellow leadership contender Lisa Raitt, who was trying to improve her French.
O'Leary stated that he was taking French lessons, and promised to learn French in time for the next federal election.

On 18 January 2017, O'Leary officially entered the Conservative leadership race.
That same day, his former Dragons' Den co-star Arlene Dickinson stated that she found O'Leary to be too "self-interested and opportunistic" to be qualified for the office of prime minister.
In response, another former Dragons' Den co-star, W. Brett Wilson, endorsed O'Leary, highlighting differences between O'Leary as a businessman and his TV persona.

On 1 February 2017, O'Leary posted a video of himself shooting in a Miami gun range.
It was removed from Facebook out of respect for the funeral for three victims of the Quebec City mosque shooting on that day.
It was also revealed that he was in New York promoting one of his business ventures when this occurred.
O'Leary later apologized for the timing of this post.

Throughout his run for the leadership of the Conservative Party of Canada, O'Leary was compared in the press to U.S. President Donald Trump.
Commentators noted that both were wealthy businessmen who gained greater fame as a result of appearing on reality television, prior to running for office, on a platform that included lowering taxes and regulations.
Some commentators also found similarities in what they called both men's brash, outspoken style, though various also stated that O'Leary's bluntness, unlike Trump's, was simply part of a "carefully-cultivated persona".

O'Leary has praised Trump personally, calling him "smart as a fox", but tended to dismiss comparisons to him by noting that, in contrast to Trump's anti-immigration rhetoric and specifically his pledge to build a wall on the Mexico–United States border, "I'm of Lebanese-Irish descent, I don't build walls, I am very proud of the society we're building in Canada, I think it is the envy of the planet.
There's no walls in my world.
I wouldn't exist if Canada had walls."
Other commentators pointed out the differences between Trump and O'Leary on other issues, including free trade, abortion, same-sex marriage, marijuana legalization and the future of NATO.

O'Leary was a frontrunner in the polls throughout most of his run.
Nevertheless, he dropped out of the leadership race on 26 April 2017, stating that, though he still thought he could win the leadership election, a lack of support for him in Quebec meant that it would be difficult for him to beat Trudeau in 2019, and that it would thus be "selfish" of him to continue.
On dropping out, he endorsed Bernier, considered the other main frontrunner for the position. (
Andrew Scheer eventually won the leadership election, narrowly edging out Bernier.)
Following Stephen Harper's resignation as leader of the Conservative Party of Canada, O'Leary attended Conservative party gatherings in February and May 2016, leading to public speculation about whether he would run for 2017 leadership election.
In February 2016, Maxime Bernier, a Conservative Quebecois politician, criticized O'Leary, calling him a "tourist" for wanting to be prime minister without being able to speak French. Bernier later explained that he wanted all leadership candidates to learn French and praised his fellow leadership contender Lisa Raitt, who was trying to improve her French. O'Leary stated that he was taking French lessons, and promised to learn French in time for the next federal election.
On 18 January 2017, O'Leary officially entered the Conservative leadership race. That same day, his former Dragons' Den co-star Arlene Dickinson stated that she found O'Leary to be too "self-interested and opportunistic" to be qualified for the office of prime minister. In response, another former Dragons' Den co-star, W. Brett Wilson, endorsed O'Leary, highlighting differences between O'Leary as a businessman and his TV persona.
On 1 February 2017, O'Leary posted a video of himself shooting in a Miami gun range. It was removed from Facebook out of respect for the funeral for three victims of the Quebec City mosque shooting on that day. It was also revealed that he was in New York promoting one of his business ventures when this occurred. O'Leary later apologized for the timing of this post.
Throughout his run for the leadership of the Conservative Party of Canada, O'Leary was compared in the press to U.S. President Donald Trump. Commentators noted that both were wealthy businessmen who gained greater fame as a result of appearing on reality television, prior to running for office, on a platform that included lowering taxes and regulations. Some commentators also found similarities in what they called both men's brash, outspoken style, though various also stated that O'Leary's bluntness, unlike Trump's, was simply part of a "carefully-cultivated persona".
O'Leary has praised Trump personally, calling him "smart as a fox", but tended to dismiss comparisons to him by noting that, in contrast to Trump's anti-immigration rhetoric and specifically his pledge to build a wall on the Mexico–United States border, "I'm of Lebanese-Irish descent, I don't build walls, I am very proud of the society we're building in Canada, I think it is the envy of the planet. There's no walls in my world. I wouldn't exist if Canada had walls." Other commentators pointed out the differences between Trump and O'Leary on other issues, including free trade, abortion, same-sex marriage, marijuana legalization and the future of NATO.
O'Leary was a frontrunner in the polls throughout most of his run. Nevertheless, he dropped out of the leadership race on 26 April 2017, stating that, though he still thought he could win the leadership election, a lack of support for him in Quebec meant that it would be difficult for him to beat Trudeau in 2019, and that it would thus be "selfish" of him to continue. On dropping out, he endorsed Bernier, considered the other main frontrunner for the position. (Andrew Scheer eventually won the leadership election, narrowly edging out Bernier.)
Kevin O'Leary