Ukip has proved it is as dangerous to Labour as the Tories, after it elected it first MP and came within a whisker's breadth of depriving Labour of a seat.
Douglas Carswell won the Clacton by-election with 21,113 votes, in a crushing defeat for Tory candidate Giles Watling, who won just 8,709 votes.
The Conservative share of the vote was down from 53% to 24.6% on a turnout of 51.2%.
In a dramatic night, Ukip also forced a recount in Heywood and Middleton, where Labour's Liz McInnes narrowly defeated Ukip's John Bickley by just 617 votes on a turn-out of 36%.
The Labour vote was actually down from 18,499 votes on election night in 2010, when an unpopular Labour government was ejected from government, although it slightly improved its percentage of the vote from 40.1% to 40.9%.
The vote was proof that while Ukip is much more dangerous for the Tories, it is also a real threat to Labour. Heywood and Middleton is a safe, industrial Labour seat and the closeness of the result will terrifying party officials.
It also suggests that either there is no Labour core vote anymore or that Ed Miliband is unable to get it out.
The only ray of hope preventing panic in the Tory ranks comes in the form of the upcoming by-election in Rochester and Strood, where former Tory MP Mark Reckless is also forcing a vote on his switch to Ukip.
In Clacton, the Conservatives had the excuse of Carswell's personal popularity and the uniquely favourable demographic make-up of the seat, which tallies precisely with the voters Ukip most appeals to.
In Rochester and Strood neither of those elements apply and the Tories are pouring resources into the seat in a frantic bid to keep it.
But a Survation poll for The Mail on Sunday last weekend put Reckless nine points ahead.
If the seat falls to Ukip, it could trigger a domino effect of other Tories switching to the party. Ukip sources suggest other converts would not need to go through a by-election if there are less than six months left before the general election.
Carswell is not technically Ukip's first MP. Bob Spink switched to the party from the Tories without a by-election in 2008, although he had to sit as an independent and was voted out the Commons in 2010.
But having a first elected MP in the Commons is a game-changer for Ukip and brings the party an element of respectability for the first time.
It is also proof that a vote for the party can lead directly to the election of a Ukip MP, flatly disproving the Conservative message of 'vote Farage, get Miliband'.