Everyone I know supports the carbon tax.  We've had one for years here in BC.  However I wouldn't presume that because I know people who support something that they represent everyone otherwise I'd have to believe the Nanos poll is wrong because it underestimates the amount of support I am aware of.  However I know people exist outside my circle so I am sure there are people who don't support a carbon tax as well as those who are unsure.  
And the polls aren't always wrong - Clinton did get 3M more votes than Trump, which showed in the polling  - but the polling didn't divide it out properly by voting district to get accurate election results.  Gerrymandering does make an extreme difference hence the reason politicians have been so interested in using it in the US.