The Mt Roskill byelection could wreck Labour.
Oh but Mt Roskill's Labour's seat - look at Phil Goff's majority. Governments don't take seats off oppositions in byelections - look at history.
But National won Mt Roskill's party vote last election by more than 2000 votes. That's a win by 6 per cent. Mt Roskill had more National voters than Labour ones. That's a bad start for Labour.
Also, low turnout plagues byelections. It can be as little as half that of the general election. That low turnout can dramatically skew the result. I suspect National voters are more likely to vote in Mt Roskill than Labour ones.
And yes the Greens with their new love-in with Labour aren't standing a candidate, but that makes Labour look weak and desperate.