Prime Minister Theresa May and Labour leader Jeremy Corbyn questioned by a live studio audience and Jeremy Paxman.

The Labour leader faced tough questioning about his past alliances and views but remained calm and confident throughout.

May was laughed at and heckled by the audience over her manifesto pledges but kept her nerve.

Corbyn emerged ahead in the biggest TV event of the general election campaign.

LONDON — A series of polls over the past week have shown Labour and its leader Jeremy Corbyn, closing the gap with Theresa May and the Conservatives in the race for Downing Street.

There are several possible reasons for this: Labour's popular manifesto policies and Theresa May's controversial social care plans and subsequent U-turn almost certainly contributed strongly to a shift in public perceptions.

However, there is an another simpler explanation:

Ofcom rules

Most British people don't pay much attention to politics outsider of election time. Occasionally something a politician says or does will be significant enough to rise up in into the general public consciousness, but by and large people's views of party leaders is filtered through the picture that is presented to them in the press and on TV.

For the past two years that picture has been largely negative. There is a good reason for that. Labour has spent those two years engaging in what has felt like an apparently unending leadership crisis, while polls have put Corbyn's party up to 24 points behind the Tories. The coverage of Labour has been mostly negative because there has mostly been negative things to cover.

However, that was all brought to an end when Theresa May called a snap general election. Not only did May's decision force Labour's warring sides to come together to fight a common enemy, but it has forced broadcasters to give equal coverage to Corbyn's party under Ofcom election rules. After a year in which the prime minister and her management of Brexit has so dominated political coverage in Britain, Corbyn has suddenly been put on an almost equal footing.

The public have liked what they've seen

Simply being put in front of the cameras isn't enough by itself. You need to have something to offer. And for the first time since he became leader, Corbyn has had that something.

In last night's Channel Four/ Sky News "Battle for Number 10" debate, Corbyn was relaxed, confident and increasingly fluent throughout both the studio Q+A and the interview with Jeremy Paxman.

Whereas in the past Corbyn has become irritable and even aggressive under hostile questioning, last night he was a picture of calm despite a barrage of questions about his alleged support for the IRA, his opposition to the Falklands War and even his opposition to the monarchy.

Questions that might have floored other politicians seemed to bounce straight off as he kept his composure throughout. Paxman, who was once the most feared interviewer in politics, barely laid a finger on the Labour leader who at times smiled and joked with the former Newsnight host. In politics tone always matters as much, if not more than, content and last night Corbyn's performance was tone-perfect.

Watch Corbyn's response to a former Labour voter:

Theresa May has faltered

Theresa May was heckled and laughed at by some audience members. Stefan Rousseau/PA Wire/PA Images

The same cannot be said for the prime minister who last night put on a strained performance in front of the cameras. There were no knockout blows and she received big applause for insisting that she would walk away from Brexit negotiations rather than accept a bad deal, but this was no vintage performance from the prime minister.

Faced with questions about her U-turn on her social care plans and cuts to school funding, May struggled to defend her position. At several points, she was heckled and even laughed at by the audience as she fell back on her anti-Corbyn attack lines.

Watch May heckled over School funding cuts:

Theresa May is heckled by members of a live TV audience while discussing education budgets. #BattleForNumber10 pic.twitter.com/D2SMa78CC9 — TUCO Angel Eyes (@Wild_West69) May 29, 2017

It could have been much worse for the prime minister. There were no major errors and the lack of any head-to-head debate with Corbyn means that viewing figures are likely to have been much lower than they were for TV debates during previous election campaigns.

But when you have based your entire campaign on comparing your own leadership qualities with that of your opponent, that needs to be clearly demonstrated to the public when the two of you are put up together on national television.

Last night that simply didn't happen. At best the event was a score draw for the two leaders. At worst, May came off a poor second.

Watching the two leaders together it became instantly clear why the Conservative campaign was so keen to avoid televised debates. May's popularity, such as it is, has depended largely on her own perceived leadership qualities, compared to the apparent shortage of those qualities in her opponent. Last night that perception was put under strain. The Conservative campaign will hope that this is the last time it is allowed to do so.