It was, he told National Observer, one of his “signature accomplishments" as the former federal conservative MP for Barrie.

The purpose of the project was to support farmers in the Lake Simcoe watershed region to help improve the water quality and make the lake “as pristine as it was in the 1950s,” Brown recalled.

Almost five years ago, Patrick Brown petitioned the federal government to help fund the clean-up of Ontario’s Lake Simcoe — which he calls the province’s “environmental jewel.” At the time, phosphorus levels in the lake were too high and water levels were the lowest they had been in 50 years.

In January 2018, he resigned as party leader after CTV reported that two women had brought forward allegations of sexual assault against him. (Brown is fighting CTV’s “negligent reporting” in court and denies the allegations.) A month later he was removed from the party caucus. Then, in October, he was elected as mayor of Brampton .

A lot has happened since then. Brown made history when he became leader of the Ontario Progressive Conservative party in May 2015 and unveiled a party platform that supported climate change, gay rights and the fight against Islamaphobia — topics not traditionally supported in modern-day Canada's conservative politics.

Brown remembers when Preston Manning, the former federal conservative leader, told him that at the very root of the word conservative was both the word and the idea “to conserve.”

After all, he says, former conservative Ontario Premier Bill Davis — whose endorsement helped Brown win Brampton’s mayorship race — created the first provincial ministry of environment. Conservative Prime Minister Brian Mulroney — whom Brown counts as a friend — negotiated the acid rain agreement. And the right-leaning government in Quebec is committed to the fight against climate change.

There’s a history of conservative environmentalism in Canada and around the world that people have forgotten about, Brown says, sitting back on a couch in a sixth-floor office at Brampton City Hall, where he works as mayor of Canada’s ninth largest city.

“It would’ve been very different if I had been premier of Ontario,” Brown says without hesitation. “I would have been a conservative partner with the federal government, trying to combat climate change.”

And if Alberta’s upcoming election ushers long-time conservative and staunch carbon-tax opposer, Jason Kenney, into office, that will make four major Canadian provinces in a contiguous geographical swath of middle Canada from Ottawa to the Rockies that have opted out of the national climate plan.

Doug Ford's first decision after becoming premier in June was to pull Ontario out of the joint cap and trade program with Quebec and California. Saskatchewan’s conservative premier, Scott Moe, refuses to implement carbon pricing and has put in its place an alternative. Manitoba’s Tory premier, Brian Pallister has also been reluctant to join the national scheme.

His exit spurred a domino effect of conservative governments veering away from Prime Minister Justin Trudeau’s plan to reduce carbon emissions, which includes imposing a carbon tax on any province that doesn't have their own emissions reduction scheme in place.

Brown’s sudden exit — which he calls a "coordinated political assassination" — wasn’t just noteworthy because it resulted in a change of leadership at the top of the Ontario PC party, ultimately giving way to Premier Doug Ford. In many respects, Brown’s departure marked the beginning of the end of a bipartisan national effort to put a price on carbon and fight climate change.

As a backbench politician in Ottawa, Brown knew he had to support the direction of the leader and the flow of his party's politics. Innately though, he knew that when the leadership opportunity presented itself he would be more outspoken on the issue of environment.

“I don't know when it happened or how it happened, but modern conservatism all of a sudden seemed to take a different approach where environment wasn't considered a conservative issue,” Brown said. “They stuck their head in the sand on the issue of environment, and I thought that was inconsistent with the history of the party.”

That opportunity came when Justin Trudeau won the 2015 federal election and signalled his intention to have a national climate accord.

“I wanted Ontario to be on the right side of history,” Brown said. In hindsight, he says, the March 2016 policy convention where he first endorsed the federal carbon pricing plan as leader of the Ontario PC Party was the moment his downfall began.

According to his book “Takedown: The Attempted Political Assassination of Patrick Brown,” Brown was initially hesitant to announce a climate change strategy that included carbon pricing (and was revenue neutral) in front of 1,700 unsuspecting party delegates. He wanted the party on his side, and decided to bring it up at a caucus meeting preceding the convention. The caucus included prominent Ontario Tory politicians now in Ford’s cabinet. At the time, Brown writes, they were all “overwhelmingly in favour of supporting carbon pricing."

The idea for a surprise public endorsement of carbon pricing came from members of Brown’s inner circle — the same members he credits with his ousting in his book. Dan Robertson, his deputy campaign manager at the time, wanted people to be shocked by Brown announcing that he was Canada's first conservative leader to support a carbon tax. It was a good "communications tactic," Brown writes. But "as a means to start a serious conversation, it backfired terribly. It caused the party internal agony and division.”

Patrick Brown, former leader of the Ontario PC party, speaks to National Observer's Fatima Syed about how a "coordinated effort" destroyed his chance to become premier. Photo by Nick Iwanyshyn

In the lead up to the convention, Brown says he knew that supporting carbon pricing would be controversial within the conservative movement, but he believed it to be “the right thing to do.”

“You don’t take public policy decisions to please the loudest voices in the room. You take public policy positions which you believe are in the best interest of your country,” he told National Observer. “And I didn't think I was being inconsistent with the roots of conservatism. I actually thought I was taking us back to the roots of Bill Davis and Brian Mulroney.”

Still, the reaction at the convention was pivotal, he recalls both in person and in his book. “There was a gasp from the crowd. One person wailed “NOOOOO!” Jason Kenney, who attended the convention, walked out of the room,” he writes.

But his caucus at the time stood by his side. Brown told The Globe and Mail after his announcement that support among his MPPs was “practically universal.”

MPP John Yakabuski, now minister of natural resources, was quoted in the same article as saying that the only way to reduce carbon was to "put a price on it."

"This is a new party, these are new times," Yakabuski said at the time. "We are making it clear that the direction we're taking out there is one that people are going to stand up and take notice."

MPP Steve Clark, now Minister of Municipal Affairs, said it was the right time for Brown to announce his position, because it would give the Ontario Conservatives a stronger footing to fight the Wynne government's cap-and-trade legislation.

"I think he wants to make sure as a leader that we just don't oppose and just don't sit in the House and say, 'No, no, no,’” Clark told The Globe and Mail. “What better place to start the conversation than at the convention.”

Two years and three months later, the same members of Brown's caucus would be standing by Doug Ford's removal of climate action policies in Ontario.

How Brown's resignation gave way to 'the hard right in the conservative movement'

Brown is the first to say that he made mistakes: he was trying to change the nature of the conservative movement overnight and that was, as subsequent events proved, an impossible task.

“I could have done more work to try to bring the party along with me on this,” he said, setting out a list: he could have met with riding presidents, with nominated candidates, with grassroots party workers. He could have had “a ferocious debate,” he writes in his book, rather than “dictating the policy on carbon pricing.”

They should have done that because the party had grown twenty times in size since he took the mantle of leader, he writes: “There were more moderate voices in the party that would have offset the naysayers and climate dinosaurs.” At the time, Brown trusted that the Ontario PC Party’s new recruits and nominees were on board with his climate plan; he made sure to talk to them all about it, especially the high-profile candidates. “It’s the leader that sets the direction of their parties,” Brown said, and repeated again that he believed he was doing the right thing.

“Everyone who was nominated when I was leader of the party shared my perspectives at the time,” Brown said. These new recruits include now Minister of Environment Rod Phillips and Attorney General Caroline Mulroney — both of whom are now leading the charge in Doug Ford’s fight against the federal carbon tax.

“The old hard line party members, they might've had a visceral reaction to a carbon price, but we had brought so many new members into the party that, I believed, the climate dinosaurs in the party were becoming insignificant,” Brown said.

Patrick Brown told National Observer that all candidates recruited under his leadership, including Ontario Environment Minister Rod Phillips, supported his carbon price plan. Phillips is seen here answering questions from the media about the cancellation of cap and trade on Oct. 3, 2018. Photo by Carlos Osorio

It was a "fairly extensive repositioning of the conservative platform," said Mark Winfield, a political scientist and professor of environmental studies at York University, and it made Brown "vulnerable."

Winfield said that Brown was the latest in a succession of conservative leaders who tried to move the party more towards the political centre, in part because the base was "too old, too male, too rural, too angry." Yet every one of them faced internal revolts, beginning with Larry Grossman in 1985 to John Tory in the early 2000s and now Brown.

"He was trying to drag his party into a more moderate position and there were definitely significant forces in that party that did not want to go there," Winfield told National Observer in a phone interview.

Brown is reluctant to draw a direct link from his stance on climate change to his ousting but now recognises the red flags. To start, his chief of staff, Alykhan Velshi, was a political strategist who worked for Kenney when he was a cabinet minister in Stephen Harper’s government, and led the Ethical Oil movement. He convinced Brown in his interview that their differences on climate change would not be a problem — a conversation, Brown now said, which led him to make "a very poor decision in hiring him;" Velshi abandoned Brown on the night the allegations surfaced.

But, ultimately, Brown blames the CTV report on the sexual allegations against him. It permitted “the hard right in the conservative movement to take the reins of the party" and remove his pro-climate stance from the party.

Without naming any names (Brown kept repeating “any members who joined when I was leader"), Brown defined “hard right conservatives” as those who “prefer inaction on the environment.”

“I’m just not sure they believe in climate change,” he said. “The reality is if you believe in climate change, you want to do something about it. If you don't believe in climate change, then mechanisms to control carbon would seem pointless.”

“I think you can skirt around the issue, but it ultimately comes to do you believe that we need to do our part on climate change or you don't?” he added.

Patrick Brown, former leader of the Ontario PC party and mayor of Brampton, speaks to National Observer in his office. Photo by Nick Iwanyshyn

Exit polls in June suggest Brown would have just as likely carried enough ridings to become Ontario’s next premier, even after the allegations that forced him to quit as leader and with his sensible climate policy intact.

The difference, of course, was that when Ford came to power, he quickly reversed the Ontario conservative stance on climate change. His very first policy decision as premier was to cancel the province's cap and trade program, 758 green energy contracts and a nearly-completed wind farm. Soon after, he launched a constitutional challenge against the federal carbon tax.

When the so-called conservative “resistance” against carbon pricing began in summer 2018 after Ford’s election, Brown says he wasn’t surprised.

“I wasn’t surprised because I knew those were the sentiments of the hard right,” he said. “Those were the elements in my own party that I had battled.”

Manitoba Premier Brian Pallister supported a version of carbon pricing when Brown was still leader, but shortly after he resigned, Pallister changed his government's position on climate change too. “Manitoba wasn’t going to be the only remaining proponent,” Brown says.

Political experts agree that Ford's election "emboldened" the conservative anti-carbon price movement across Canada. He "clearly led the charge with a very in-your-face, flash-and-burn kind of attitude" that allowed other provinces to fall in line, said Jessica Green, associate professor of political science at University of Toronto.

"Correlation is not causation, but it became easier for other politicians who were on the fence to voice their concerns once Ford declared all-out war on climate policies in Ontario," Green told National Observer in a phone interview.

Had Brown stayed leader, "barring some disaster," the basic national consensus that underpinned the pan-Canadian framework to fight climate change would've stayed in place, Winfield said. "There’s no question (Ford's victory) was a game-changing event in terms of the conversation on climate change and carbon pricing."

"The conversation has completely altered relative to where we stood in June 2018, when the only outlier (to the federal carbon pricing plan) was Saskatchewan," Winfield added. Ontario, alone, saw "a stunning shift," he said, moving from a position where all three major political parties supported some sort of carbon pricing. "It all virtually changed overnight."

Today, any Ontario conservative members who supported Brown’s climate plan “aren’t involved anymore,” Brown said. If they still share his pro-climate change perspectives, Brown believes they’re not permitted to share their views publicly — after all “politics is a team sport and they respect the wishes of the leader.”

“The leadership has said that they don't support carbon pricing and the debate is over,” Brown said. “Right now, if an MPP criticizes the premier, they're out of the party.”

“Look at Amanda Simard.”

(Simard was a rookie Conservative MPP who spoke against Ford’s decision to eliminate the French language commissioner. She has since left the Ontario PC party and now sits as an independent.)

The Conservative Party needs to 'catch up' on the issue of climate change

In his almost hour-long interview with National Observer, Brown says Doug Ford’s name twice — otherwise referring to him exclusively as “the premier.”

Brown says he is choosing “not to be a critic from the sidelines,” but briefly — and guardedly — makes some comments. Brown wouldn’t have eliminated the Environmental Commissioner of Ontario. He wouldn’t have removed environmental protections surrounding development and water across the province (which Ford is proposing in Bill 66, which will be debated when the legislature returns in February.)

And, as for Ontario’s new climate plan, Brown asks bemusedly: “Do we have a climate plan?” He doesn’t hesitate to add that his climate change plan would have been “far more aggressive and ambitious.”

“I wanted carbon pricing that would have kept all funds collected from combating climate change in Ontario and instead we've got rid of cap and trade and replaced it with nothing.”

WATCH: Patrick Brown insists he can work with anyone, even political adversaries like Premier Doug Ford. The Mayor-elect says he wants what’s best for #Brampton. #ONpoli pic.twitter.com/MMNYTzPx9g — NEWSTALK1010 (@NEWSTALK1010) October 23, 2018

In the era of Donald Trump, Brown says, it may seem inconsistent to want to combat climate change — conservative ideology across North America has made opposing climate change mutually exclusive. But that, Brown says, is a misinterpretation of what societies demand. “You can't mistake the voter's desire to get rid of Kathleen Wynne with an endorsement of not wanting to have a plan on the environment,” he said. “It was not an endorsement of not wanting to have that modern, inclusive, a pragmatic approach to government.”

Brown believes that the Conservative Party — provincial and federal — will have to “catch up” with Canadians on the issue of climate change.

“Politics can change quickly,” he said. “If you’re asking me to look into a crystal ball and say how long it’s going to take or what’s going to happen? Well, if someone said to you a year ago, Doug Ford would be premier of Ontario, you would’ve laughed at them.”

Politics can change quickly, he repeated, and the policy direction of a party is set by “a leader that cares about the issue.”

And, there are leaders that care about climate change among Canada’s conservative parties, Brown said. Unclear, however, is what it’ll take for them to protect the environment.

“We’ll see,” Brown said, shrugging his shoulders.

Is it going to be a deadly forest fire that spurs conservatives into action? A destructive flood?

Brown paused. “I don’t know.”

Editor's note: This article was updated at 7:15 p.m. ET on Jan. 10, 2018 to clarify that Patrick Brown resigned in January 2018.