(CNN)The verdict of the opinion polls on the UK election debate between seven party leaders was simple enough: Between David Cameron of the Conservatives, Ed Miliband of Labour, Nick Clegg of the Liberal Democrats, Nigel Farage of the United Kingdom Independence Party, Natalie Bennett of the Green Party, Nicola Sturgeon of the Scottish National Party and Leanne Wood of Plaid Cymru, the Welsh Nationalists, there really was no clear winner. Comres for ITV, which staged the debate, had Cameron, Miliband and Farage tied first with 21% and Sturgeon close behind on 20%. ICM for The Guardian scored it Miliband 25, Cameron 24, Farage 19 and Sturgeon 17. YouGov for The Times put Sturgeon first with 28 points to 20 for Farage, 18 for Cameron and only 15 for Miliband. Back in the 1950s, UK politics was simpler: Labour and Conservatives combined took 97% of the votes. But nowadays they struggle to collect two-thirds of the national vote between them. In our anti-politics age nationalists and others have advanced and the leaders' TV debate was no gladiatorial contest with a straightforward outcome. Rather it was a cacophonous shouting match that probably gave all parties' supporters some satisfaction but which offered little new insight to the undecided voter. From a highly confused affair we can perhaps take six lessons: . As the incumbent Prime Minister, Cameron is probably wise to have refused all invitations to go head to head with Miliband alone in verbal fisticuffs. He has risked being labelled a coward for doing so but it was a tactical decision. Miliband has been given a hard time by the British media who have gloated over his difficulties in eating a bacon sandwich and presented him as an awkward geek. But Labour's leader is a perfectly capable debater. He could only gain from their confrontation. As it is, election time media exposure has already seen Miliband's ratings as a leader improve. The electoral strengths and weaknesses of the two main leaders are emerging. In an earlier clash involving separate sessions before a studio audience and in a grilling by UK TV's Grand Inquisitor Jeremy Paxman, Cameron proved vulnerable on broken promises to cut immigration, on the number of people employed on zero-hours contracts and on being too kind to the rich in his taxation policies. Miliband has looked unconvincing on how he will fund his promises to continue cutting the budget deficit and how he will curb immigration; he also is still embarrassed when questioners remind audiences how he knifed his brother David to get the leader's job. The impression so far is that Britain's voters don't much like the Conservatives despite the recovering economy but don't quite trust Labour to continue the improvement. Miliband, told by his handlers to look tough, is using the "i" word too much. Cameron is curiously short on passion. An oddity of the Seven Up debate was that many who viewed it will have no chance of voting for two of the leaders involved, Sturgeon of the Scottish National Party and Wood of Plaid Cymru. But Sturgeon's high score in the post-debate polls was significant. She was sharp and sassy. The number of seats gained by the Nationalists, currently on target to win as many as 50 of the 59 Westminster Parliament seats in Scotland, will be crucial. Last time Labour won 41 of those seats: The more the SNP take, the weaker Labour's chance of a majority at Westminster will be. Miliband says he won't form a coalition with the SNP but it could be difficult for Labour to govern without some deal with their bitter opponents north of the border. If there was a "winner" in the debate it was Nicola Sturgeon. Back in the 2010 UK election debates the clear victor was Clegg of the Liberal Democrats. Then the two main party leaders frequently found themselves parroting "I agree with Nick." By entering a coalition government with Cameron (in which the Lib Dems' insistence on raising the tax threshold for the lower paid has been a key element in increasing employment and economic recovery), Clegg surrendered the Lib Dems' previous ability to pick up protest votes. Clegg and his party have paid a heavy price for the compromises made in government, notably on student tuition fees. His debate performance was as good as any of the seven leaders but no poll gave him a rating of better than 10%. Perception is everything. In social media and studio focus groups there were plenty of plaudits for the Greens and even for Plaid Cymru's Wood but Clegg got hardly a mention. The United Kingdom Independence Party remains the joker in the pack. The party once dismissed by Cameron as a collection of "fruitcakes, loonies and closet racists" is a serious threat to the Conservatives -- and Labour -- despite the many gaffes that seemed to cost it some momentum lately. But UKIP, more than any of the others, is a personal vehicle for its leader and the debate was crucial for them. Grinning Farage's blokey saloon bar manner goes down well with studio audiences and he kept the focus on immigration. His party won't win many seats but he has ensured they can still tip the balance in plenty of contests, sometimes taking votes off the Conservatives, sometimes off Labour. Farage has always traded on the outer edge of political civilities and by insisting in the debate that immigrants were responsible for 60% of HIV cases he earned condemnation from other leaders. On social media, dominated by the young, that earned him the maximum boo count. To "win" a TV election debate you need to avoid gaffes yourself, to wrongfoot your opponent, and to offer some excitement that gives your campaign the chance to develop momentum. You need to produce vivid soundbites which will work their way into summary reports of the debates and into campaign replays. Nobody has yet succeeded in doing that in this campaign. The highly paid spin doctors employed by the three major parties are simply not worth their money. The emphasis has been on sound defense: Nobody has yet scored an exciting goal. As the campaign moves on, chances will have to be taken. READ: Fish, bacon and beer: The real issues in Britain's election .
No clear winner in opinion polls after first UK election debate between seven party leaders . Robin Oakley says David Cameron and challenger Ed Miliband did well, but there was little insight for voters .