Hi, argyle5663. Interesting comment.
"Our mainstream parties have essentially kept a lid on the immigration debate for two or more decades..."  Really?  Systematically, consciously?  And how long?  The "two or more decades" really caught my eye. Would you believe 15 decades?  Because Canadian Immigration figures have increased every decade over the past 150 years. As much as 1.5 million, in some decades.  That's a lot of sustained "lid" pressure! And it certainly is taking the population long enough to say, "Enuff already!"  It's like the non-issue of racial violence before that 1920 Presidential Election.  It took roughly another 40 YEARS for people to "We won't stand for it!"  Politicians only care when people care, it seems.

"It will be interesting to see how long our illustrious mainstream politicians can defy gravity on this."  Our PM seems to have come down to earth a bit: fewer refugees anticipated this year than last.