Tories target Labour voters who switched to Ukip in 2015

Today, Doncaster. Yesterday, Teesside, West Yorkshire and Derbyshire. All lifelong Labour heartlands. So why has Theresa May been campaigning there?  The answer  – Conservative strategists believe they can persuade Labour supporters who switched to Ukip at the last general election to back Theresa May this time,turning those seats into a sea of blue. But with talk of a Corbyn surge, is that strategy still on track?