Have you noticed who's leading the Labour Party these days?
Corbyn is the devil incarnate to all Tory voters. Any Tory Remainers so disenfranchised with the Tories will vote LibDem, not Labour. I'm serious, I can't remotely imagine Labour will pick up any significant number of would be Tory voters whatsoever. If half the Labour voters can't stand him - what chance does he have of gaining Tory votes? Nil.
Labour have no pool from which to get any extra votes. So they'll get less than last time, for certain. The only question is whether the Tories will do even worse, but at the moment, it doesn't look like it.
The vote, IMO, will split like:
1. Labour - in constituencies where Labour will be returned come what may - but they will make a disappointing number of gains with their target seats either going to the LibDems or the Conservatives. I think that they will get fewer seats than the 2017 GE.
2. Conservatives - will win their traditional strongholds - with only a relatively few seats lost to the LibDems
3. LibDems in a few Remain dominated seats where the polling shows that there is a chance of LibDems getting a majority so therefore taking some seats from the Conservatives - but perhaps more from Labour. I do not see any chance of a Lib/Lab deal before or after the GE result.
4. Conservatives in sufficient marginals to win a majority
5. Not bothering about the SNP because that is obvious - although a clean sweep is not a given. I do most of my work in Scotland and there is more commitment to the Union than people might believe because they only hear the SNP views.
All this has become obvious to Labour who now want the election but first want/need to burst the Johnson bubble / momentum and ideally embarrass him by failing to deliver on his do or die promises. That is because a few percentage points reduced for Johnson probably makes the difference between a Labour or Tory PM. So they will run for cover - taking refuge in the 'we must stop no-deal' mantra whilst they seek to do that. They will want him to stew and look flummoxed for a while so that any gloss and feeling of drive evaporates in the minds of the voters.
I think that in private the Labour leadership must be feeling very frustrated and concerned - their current leadership have been waiting for this opportunity for many years and have been confident for years. All of a sudden it could go pear shaped as they get squeezed between both the Conservatives and the LibDems in a buoyant state - but they have little choice but to take their chance.
If 4. does not happen then a post GE minority Labour government will at least see constraints placed on McDonnell's excesses. There will be utter paralysis - same if it is a minority Conservative government.
So the games in the coming weeks will be interesting. People like to think that Johnson is a clown - but some people behind him are not and therefore some of this do or die mantra must be against some intended ploy. Having read the new legislation it seems 'watertight' to me - but there must be some gambit that I cannot see that is going to be played now that parliament is prorogued - at least I would hope so.
If he does not win the GE then Brexit is consigned to the bin and he is toast - so his planning beyond that must be on the assumption that he will win.