Ukip caused another mini-earthquake under Westminster after the Eurosceptic party's candidate won the crucial Rochester and Strood by-election.
Conservative defector Mark Reckless is now Ukip's second MP after Douglas Carswell won the Clacton by-election in October.
The Conservatives finished second, Labour third, with the Liberal Democrats beaten to fourth place by the Green Party.
Anthony Wells, YouGov's associate director for political and social opinion polling, spoke to IBTimes UK about what the key questions from the by-election result: Can Ukip's success continue at the 2015 General Election? How damaging was this 5th-place finish for the Liberal Democrats? And does the surge in support for the Green Party present a threat from the left to Labour?