A new poll of the voting intentions of a group of 4,000 people who watched the programme dramatically propelled the Liberal Democrats into second place in the election campaign.
The poll by ITV/ComRes put Liberal Democrat support at 35 per cent, up 14 per cent.
The Conservatives were at 36 per cent, down 3 per cent compared to before the head-to-head studio debate.
Labour was at 24 per cent, down 3 per cent, and others were at 5 per cent, down 8 per cent.