The New Democrats appear to have the Liberals and the Progressive Conservatives over a barrel in Niagara Falls, a new poll suggests.

And the governing Grits face a steep hill to climb to wrest Thornhill from the Tories, according to a separate survey.

‎With voters in the two key ridings casting ballots in byelections Thursday, both opposition parties look set to win seats — shutting out Premier Kathleen Wynne's Liberals.

“In Niagara Falls, the NDP have run a very solid campaign and have gained ground every time we’ve polled,” Forum president Lorne Bozinoff‎ said Wednesday.

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· Winter byelections could set the stage for spring clash: Cohn

· High-stakes contest in Niagara Falls

Bozinoff said it seems as if “there are really no surprises” in store in solidly Conservative Thornhill.

“The campaign hasn’t really changed much since we first polled,” he said.

In Thornhill, held by Progressive Conservative MPP Peter Shurman from 2007 until 2013, PC candidate Gila Martow was at 51 per cent to 40 per cent for Liberal Sandra Yeung Racco, wife of former local Grit MPP Mario Racco.

The NDP’s Cindy Hackelberg was at 5 per cent and Green Party’s Teresa Pun was at 2 per cent.

In Niagara Falls, represented by Liberal MPP Kim Craitor from 2003 to 2013 — the NDP’s Wayne Gates has surged to 48 per cent, well ahead of former MPP Tory Bart Maves at 33 per cent and Liberal Joyce Morocco at 17 per cent. The Greens’ Clarke Bitter was at 2 per cent.

Using interactive voice-response phone calls, Forum surveyed 518 people in Niagara Falls on Tuesday and results are considered accurate to within four percentage points, 19 times out of 20.

In Thornhill, the firm polled 407 people with a margin of error of five percentage points, 19 times out of 20.

Like most pollsters, Forum uses a proprietary weighting formula, which has been shared with the Star, to more accurately reflect the broader electorate. Raw data from this poll will be housed in the Political Science Data Library at the University of Toronto.

In last Wednesday’s Forum polls of the two ridings, the Tories were at 47 per cent in Thornhill to 37 per cent for the Liberals and 6 per cent apiece for the NDP and the Greens.

Last week, the NDP led in Niagara Falls with 38 per cent to 36 per cent for the Tories, 19 per cent for the Liberals and 3 per cent for the Greens.

On Tuesday, the panicked Conservatives held a press conference at Queen's Park to complain Gates’ campaign had an army of 700 “union activists” flooding the riding to pull vote for the NDP.

Because Tory Leader Tim Hudak, who holds Niagara West-Glanbrook, hails from Fort Erie and represented part of the riding prior to redistribution, a loss in Niagara Falls would sting.

In that sense, NDP Leader Andrea Horwath may well be the only clear winner Thursday night if these public-opinion polls hold up.

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Still, regardless of the results of the byelections, Ontario’s political landscape will not be radically altered — at least in the short term.

Including Speaker Dave Levac, the Liberals currently have 49 seats in the 107-member minority legislature while the Tories have 36 and the NDP 20.

But the contests could be the prelude to a province-wide campaign this spring.