David Cameron, Ed Miliband and Nick Clegg are taking part in a special leaders' edition of Question Time on BBC1, in the final major televised event before the general election.
In his 30-minute slot, the prime minister faced questions on what benefits he would slash in order to cut the deficit, how he could be trusted with the NHS and why he won't raise the prospect of forming another coalition government.
But while the audience seemed very engaged with the questions and answers, people on Twitter seemed a bit distracted. By Cameron's sweaty lip.
As lots of people pointed out, this all harked back to Richard Nixon's performance in a televised debate with John F Kennedy in 1960 in the US.
Nixon sweated profusely, lost the debates, and the presidency.
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