Johann Hari's view of the debates:
The British media is overwhelmingly owned by right-wing billionaires who order their newspapers to build up the politicians who serve their interests, and marginalise or rubbish the politicians who serve the public interest. David Yelland, the former editor of The Sun, bravely confessed this week that as soon as he took his post, he was told the Lib Dems had to be "the invisible party, purposely edged off the paper's pages and ignored". Only a tiny spectrum of opinion was permitted. Everyone to the left of Tony Blair (not hard) had to be rubbished even when their policies spoke for a majority of British people.
Both TV debates, then, have been a very rare moment in which a slightly more liberal-left voice could speak to the public without the distorting frame of pre-emptive abuse and smears. When, for example, have you ever heard the EU defended as plainly and clearly? The window of permissible opinion was opened a little and people responded with a wave of enthusiasm. It could've been opened wider still to the Greens, say and found a receptive audience too.