I would read the chart somewhat differently.  The Tories got a huge surge when the election was announced which then flattened and has now been reversed. This surge corresponds almost precisely with a precipitous decline in the UKIP vote.

Labour, on the other hand, have been climbing steadily and consistently firstly at the expense of the Lib Dems and smaller parties, and now more recently at the expense of the Tories themselves.  May's TINA narrative has clearly been shattered and all the late breaking momentum is with the Labour.

The chart doesn't show undecided voters, but I would guess much of Labour's gain has also been due to undecided voters gradually moving into their camp as the campaign progresses.  If Labour can maintain this momentum, the election could be too close to call.

However the Tories only have a tiny majority now, so almost any victory will give them some extra seats which they will tout as an endorsement of May and her approach. In the meantime the Brexit clock is ticking and I can't see any of this strengthening the Tories hand in the negotiations.

I would expect the EU negotiating team has gamed out the consequences of no deal and will be asking themselves what the UK has to offer that would be better than that.  Given the UK has offered almost nothing to date, the mantra "no deal is better than a bad deal" applies to the EU as well.

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