Brown, 39, announced his resignation in a statement following a hastily called media conference in which he “categorically” denied the “false” allegations.
Here’s what we know so far.
What’s being said about him
In a CTV story published Wednesday, two women accused Brown of sexual misconduct that dates back to when he was a Member of Parliament (MP). The women’s identities were not revealed.
One woman said the incident happened more than 10 years ago when she was a high school student in Barrie, Ont., according to CTV.
The woman then said she met Brown at a local bar, had alcohol (even though she was underage) and then went back to his place. She said he exposed himself to her and asked her to perform oral sex, which she did for a short time, according to the CTV story.
The woman, who is now 29, called it a “controlling thing” and said Brown is a “politician preying on young girls,” according to the story.
The other woman said she was a university student working in Brown’s constituency office in 2013 when he sexually assaulted her at his home after an event she helped organize, CTV News reported.
When they were alone, he allegedly kissed her and “got on top of her,” CTV said. She described it as sexual assault.
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The woman said she did not report the alleged incident to authorities.
CTV News said it had viewed records of correspondence between Brown and the women. None of the allegations have been proven in court.
What Brown is saying
At a media conference Wednesday night, Brown denied the allegations.
“A couple of hours ago I learned about troubling allegations about my conduct and my character,” Brown said.
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“These allegations are false, categorically untrue — every one of them. I will defend myself as hard as I can with all means at my disposal. It’s never OK, it’s never OK, for anyone to feel they’ve been a victim of sexual harassment or feel threatened in any way.”
Brown said he rejected “these accusations in the strongest possible terms.” “It’s not my values, it’s not how I was raised, it’s not who I am,” he said.
Brown says ‘not resigning’ as leader, but then resigns
At the media conference, Brown said he would be back to work Thursday morning and would not resign. But hours later, he released a statement saying he is stepping down as Ontario Tory leader.
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“After consulting with caucus, friends and family I have decided to step down as leader of the Ontario PC Party. I will remain on as an MPP while I definitively clear my name from these false allegations,” Brown said in a written statement issued early Thursday morning.
He said that while the allegations are false, “defeating Kathleen Wynne in 2018 is more important than one individual.”
Sources previously confirmed to Global News Brown began working on a resignation letter following late night calls between Brown, PC caucus members and members of the party’s executive.
Senior PC staff members step down
Following the press conference, three senior Ontario PC staffers released a joint statement resigning from the party.
The first resignations were announced on social media by campaign manager Andrew Boddington, chief of staff Alykhan Velshi and deputy campaign manager of strategy Dan Robertson.
In the statement, they said they’d learned of the allegations against Brown earlier Wednesday, and upon discussing them with Brown, they’d advised him to resign.
Shortly after, Ontario PC Party press secretary Nick Bergamini and deputy campaign manager Joshua Workman tweeted that they would also resign because of the allegations.
What Canadian leaders are saying
Federal Tory Leader Andrew Scheer said the allegations are “extremely serious” and “should be investigated fully.”
“Sexual misconduct and sexual harassment have no place in Canadian society, especially within our political system,” Scheer said in a statement.
Ontario Premier Kathleen Wynne tweeted late Wednesday evening, “it is a difficult and brave thing to come forward in the way these young women have done. My government and I have been clear on the issue of sexual harassment and assault. In fact our policy and our ad were called ‘It’s Never Okay.'”
Andrea Horwath, the leader of Ontario’s NDP, said “I’m disgusted and disturbed by these sexual misconduct allegations. Patrick Brown must resign, immediately. He deserves his day in court, but no person can lead a political party in this province with allegations like these hanging over his head.”
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In a statement, Ontario PC deputy leaders Sylvia Jones and Steve Clark said, “In the interest of the Ontario PC Party we unanimously agree that Mr. Brown cannot continue serving as the leader. Mr. Brown is entitled to a legal defense and due process, but he cannot lead us into an election as a result of these allegations.”
Conservative MPP Lisa MacLeod released a statement on the allegations saying she “will not tolerate abuse and harassment” and will do everything in her power to fight against it.
“My heart goes out to the women who have been impacted by this behaviour,” the statement said. “It takes courage to come forward and makes these claims.”
Brown’s political career
Brown had previously been leading in the polls ahead of Ontario’s June 7 provincial election.
He was first elected as federal MP in 2006 as part of the Conservative government after serving as a Barrie city councillor. He was re-elected twice, in 2008 and in 2011.
During his time in Ottawa, Brown served as a backbench MP in Stephen Harper’s government and has been frequently criticized by political opponents for voting in favour of reopening the abortion debate.
He won the PC leadership in 2015, beating long-time Ontario legislator and favourite Christine Elliott.
Who will replace him?
It is unclear who will replace Brown and how the new leader will be chosen.
But even before Brown’s decision to resign, speculation began swirling as to who might replace him. MacLeod, former Conservative MPP Christine Elliott and Ontario MPPs Monte McNaughton and Vic Fedeli were mentioned as possible candidates to take on Wynne in June.
— With files from the Canadian Press