~10% support overall. However, that's 21% of Conservative voters and 1-3% everyone else. So it's beyond fringe for everyone else, but maybe not as much for Conservatives.
Note that despite the headline, The Ipsos poll also says 80% polled would never vote for Canada to become part of the United States, while the Leger poll says 82% would not like Canada to become the 51st state. These are 3 of the standard pollsters that regularly get commissioned by TV and newspaper to do polls for them, and I have no reason to suspect that the polls are "cooked". 338 rates Angus Reid as B+, Ipsos as A, and Leger as A+.