Leading Tory eurosceptic says Carswell's decision doesn't make sense after Cameron's EU referendum pledge.
The party's best hope of defeating the defector lies in winning tactical support from centrist voters.
The MP for Clacton has defected from the Conservatives to Ukip.
Farage needs to explain why he could prevent the referendum he has always wanted.
There is certainly space in British politics for a party beyond the edge of Labour, but a left-wing alternative has yet to emerge.
Rather than choosing a former Ukip leader as their candidate in South Thanet, the party should have selected a liberal figure capable of winning tactical votes.
The Labour MP for Wigan talks about the need for her party to appeal to people who feel “very insecure” and “lack control over their own lives and communities”.
Ukip leader plans to run in Tory-held constituency where his party currently polls first.
The most detailed analysis yet of Ukip’s performance shows its threat to the Labour Party.