The poll by Ipsos Reid puts the Liberals at 41 per cent support among decided voters and the Progressive Conservatives at 31 per cent support.
It places the New Democrats at 25 per cent support and the Green Party at three per cent.
The poll marks a major shift from recent surveys that had the Liberals and Conservatives in a dead heat, raising the prospect of Ontario's first minority government in 26 years.
In July, an Ipsos Reid poll showed the Tories with an 11-point lead, but the latest numbers suggest that support has slipped significantly over the last three months.
Ipsos Reid says its poll suggests the Liberals are headed back to government, potentially with a majority.
The poll surveyed 1,020 adults by telephone between Sept. 30 and Oct. 3.
The results are considered accurate within plus or minus 3.1 percentage points, 9 times out of 10.
The poll was conducted for Global News, CFRB NewsTalk 1010 and the Ottawa Citizen.
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