UKIP are a spent force and are likely to really struggle this time around. Their voters are likely to desert them in droves as firstly they were a one trick pony that have achieved what they set out to do and secondly like him or loathe him Nigel Farage was a fairly charismatic leader and now that he has gone so will his voters
That was always likely to happen, but I don't think new Tory voters fresh from UKIP are as solid as May seems to think they are.
On the issue of Brexit, May was originally a remainer, so there's some scepticism amongst UKIP voters regarding the direction she'll go in during negotiations.
She seems to be taking a hard line, but I think this rhetoric is focused on:
1). Winning over UKIP voters
2). Bluffing in front of the EU to win more favourable terms
I don't think she actually wants a "hard" Brexit. She would prefer to retain some integration if it results in a better trade deal. But she's making clear that she will cut all ties if she has to.
That's the key difference. May would reluctantly shift the UK away from the EU, whereas UKIP actually want the cleanest break possible.
There are other policies too: Foreign aid cuts, the suppression of Islamic practices, harsher immigration stances, even lower tax cuts and so on.
I think a lot in the Conservative manifesto will be accepted by moderate conservatives, but really grind against those further to the right. This could result in a lot of protest voting, where they stick with UKIP even though they are indeed a spent force.
And this may be amplified by the apparent weakness of the opposition. No voters on the right appear genuinely concerned about Corbyn getting into power, so there's less urgency to vote Tory to make sure he stays out.
I'm looking at the older vote in particular. After these cuts to pensioner and social care funds, many pensioners may think twice about switching, or decide not to vote at all.
May will win, but when all is said and done, the only gain might be a stronger mandate.