Ontario's New Democratic Party has been dealt a blow after a prominent community activist and former supporter of Andrea Horwath announced she is jumping ship to run for the Liberals in the party leader's own Hamilton Centre riding.

Deirdre Pike, a senior planner with the Hamilton Social Planning and Research Council and Hamilton Spectator freelance columnist, announced her surprise intentions this weekend in her final column with the paper.

The 55-year-old LGBTQ and social justice advocate said she was swayed by the Liberals' work on anti-poverty initiatives, specifically around minimum wage – a file the left-wing NDP has been criticized for not championing. "I have stood beside Andrea in solidarity at many rallies over the years as we were on the same side of so many issues. Now our paths have diverged," Ms. Pike wrote in her column. "Her silence on poverty is disheartening."

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She says the response has been largely supportive, but acknowledges that there has also been criticism from former peers in the NDP camp who see the move as a betrayal.

"I am hoping that the folks who will be disappointed in me for sure, who will see me as leaving their camp, will at least see me as a … worthy opponent and someone with good intentions," she said Monday.

NDP spokesperson Rebecca Elming said Monday that while the party wishes all candidates well, Ms. Horwath was unavailable to comment.

Political observers have noted Ms. Horwath has an opportunity to benefit from political upheaval at Queen's Park. Just weeks after the gas plant trial hurt the Liberals and the ousting of PC Leader Patrick Brown amidst sexual misconduct allegations, the NDP has the best chance it's had since Bob Rae won in 1990, said Henry Jacek, a political science professor at McMaster University.

It would be "mind-boggling" if Ms. Horwath lost her seat, said Mr. Jacek. After becoming a city councillor in 1997 and switching to provincial politics in 2004, Ms. Horwath has held the Hamilton Centre seat since the riding's creation in 2007, and the title of party leader since 2009.

Mr. Jacek believes part of Ms. Pike's motivation is the opportunity to bring more visibility to the issues she supports.

"She's campaigning against the leader….she's going to get a lot of attention for her issues. She's willing to risk being alienated from the New Democrat Party and her NDP friends – and I'm sure some of them are going to give her a lot of flak. It's a courageous step."

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Tom Cooper, executive director of Hamilton's Roundtable for Poverty Reduction, said he is looking forward to the policy dialogue the race will bring.

"It creates a dynamic in the community that's going to be uncomfortable for some people. But at the end of the day if we can talk more about the need to reduce poverty and to commit resources to reducing inequality, then it's going to be good in the long run," he said.

Peter Graefe, another political science professor at McMaster whose research focuses on the NDP, says the Hamilton Centre riding is likely one the Liberals have their eye on long-term – particularly amid changing demographics and real estate value in the rapidly evolving city.

But while Ms. Pike is well-known for her advocacy work in Hamilton, Mr. Graefe doubts she's enough of a household name to topple Ms. Horwath.

The next step for Ms. Pike will be to officially seek candidacy at a riding association meeting this month.

"After all I've heard since the weekend, I think it's winnable. I do," Ms. Pike said.