Ukip is hoping to capitalise on this momentum to win the next by-election in Rochester and Strood, prompted by the defection of Tory MP Mark Reckless. But history shows that the Tories have quickly snatched back some seats they have lost in by-elections at the following national elections.
Election expert Lewis Baston told the Huffington Post UK: "It's not very unusual for the government party to regain such losses, particularly if it is winning the election nationally."
Baston, a senior research fellow at the Democratic Audit research group, stressed that Carswell was likely to survive as he had won by an "exceptionally large" margin and built up a personal vote.
But with speculation rife about how many extra MPs Ukip could get before the 2015 general election, here are five seats the Tories snatched back just months after their own by-election losses.