An anti-Ukip Twitter campaign has gone viral as social media users warned other voters not to let the Eurosceptic party "sleepwalk" into holding the balance of power.
The 'We Are The 85%' meme, referencing how Ukip hold 15% of the national vote in latest polling, came as Tory defector Mark Reckless regained the Kent seat with a majority of 2,920 to be the party's second MP.
The viral campaign began Friday morning, by anti-fascists Hope Not Hate, and used the hashtag #NotVotingUkip:
I'm #NotVotingUKIP cos I don't have a problem with immigrants, gays & disabled people. I love the NHS & am more intelligent than a dishcloth— Mary Foy (@marykfoy) November 21, 2014
#NotVotingUKIP because my grandfather fought fascists in the war and I'd rather not urinate on his memory.— Greg Blackman Music (@GregBlackmanUK) November 21, 2014
#NotVotingUKIP because I'm not a sheep who believes that foreigners are the thing wrong with our country. It's the men in suits.— India (@IndieAfc) November 21, 2014
#NotVotingUKIP Because I won't vote for a party that could conceivably have the Daily Express as their manifesto.— Christian DeFeo (@doctorcdf) November 21, 2014
I'm #NotVotingUKIP because I know that it's wrong to blame people in minorities for my own, and other people's, laziness and greed.— Amber (@AmberKeates) November 21, 2014
#NotVotingUKIP because I know better than to blame this country's issues on immigrants, single parents and gay people.— Joelle (@Joelle_o) November 21, 2014
Ukip leader Nigel Farage said he would be "very surprised" if more Tory MPs did not now choose to jump ship and join his party in the run-up to the general election next year.
Among the Conservative high command, there was some relief that the final margin of defeat was narrower than many commentators had been predicting.
In the aftermath of the vote, a number of prominent Tory Eurosceptics - including John Baron, Philip Davies and Stewart Jackson - came out to declare their continuing allegiance to the party.
The result was nevertheless another wounding blow for Cameron, following the victory of Mr Reckless's fellow Conservative defector Douglas Carswell in Clacton, Essex.
Farage said the result - in Ukip's 271st target seat - showed that his party was now capable of winning anywhere in the country.
"We have beaten the governing party of the day in this sort of life-and-death struggle. It represents a huge, huge victory," he told Sky News.
"I would be very surprised, given where we are, if there weren't more defections between now and the next general election.
"They won't happen today, they won't happen tomorrow, but over the course of the next few weeks people will be thinking and perhaps some of them saying to themselves 'You know what, I have got a better chance of winning on a purple ticket than I have on a blue ticket'."
All three main parties saw their share of the vote fall compared with the last general election, with the Lib Dems down by 15.39%, the Tories by 14.39% and Labour by 11.7%.
Ukip's first directly-elected MP, Douglas Carswell, predicted the party could win "dozens" more seats and suggested it could replace Labour as the main opposition by offering a modern version of the "free market, economically liberal" administrations of William Gladstone in the 19th century.
Writing on the Daily Telegraph website, Carswell said: "If Ukip can win in Rochester, the 271st most Ukip-friendly seat in the country, Ukip can win in dozens of other seats too."
Ukip's victory in Rochester showed that, by appealing directly to ex-Labour voters, the party has an opportunity to "undo the tragedy of the 1920s", when Labour became the second party of British politics, he said.
"So much of Britain is now run in the interests of various vested interests, there is an extraordinary opportunity for a new, free market, economically liberal party committed to far reaching, radical political reform," said Carswell. "Think of it as Gladstone dotcom."