Tavish Scott: Ed has given the PM a hard act to follow MESSRS Miliband and Clegg now look unassailable. The main requirement of a political leader's speech is to keep the troops onside. I've written a few leader's speeches, briefed the press on more and even delivered them. An enormous amount of time goes into the production of political gab. This week Ed Miliband gave a highly impressive and polished performance speaking to the Labour Party conference in Manchester. He memorised the text and spoke not for the scheduled 45 minutes but just over an hour. And I accept that it is no surprise that a politician can speak for an hour. Miliband takes credit therefore for impressing his party, journalists and naturally hostile commentators. But will his performance resonate with the country? I think it will. The shambles of the West Coast rail franchise has helped the Miliband argument that the coalition has some competency issues to address. Internally, Miliband has seen off the ever-present challenge of the other Ed - Balls. The shadow chancellor was not elected by the Labour Party membership, so his vaulting ambition will have to wait. Labour certainly does not need a rerun of the Blair and Brown relationship laid bare by numerous post-government books. Ed Miliband is now unquestionably the man who will lead Labour into the 2015 UK General Election. That was not clear before his party conference. Miliband has cemented his party together against a common enemy: the Tories. Balls will have to play ball, and political journalists will have to give Miliband the benefit of the doubt. Nick Clegg too emerged from his party's conference in a considerably stronger position. The run-up to the week in Brighton was horrible. Senior party figures said he would have to go. But Clegg's personal decency and strength shone through. Kevin Maguire, associate editor of the Daily Mirror, said he could not agree with Clegg's politics but observed that Clegg was a genuine human being. So the tightrope judgment for apologising over English university fees may play out to be a strategic plus. Irrespective of the country's verdict on the Lib Dems, Clegg is back in control of his party. The appointment of Paddy Ashdown is a masterstroke. Paddy will stare down internal dissent and enliven the activist base. He is now as important for the Lib Dem chances in 2015 as Clegg. Which leaves the Prime Minister. David Cameron approaches his party conference with the ever-present shadow of London mayor Boris Johnson on the fringe. The Tories have been behind Labour in the opinion polls for months. Some Tory MPs openly back a leadership challenge. This is political madness. But against all the odds it is the Tory leader who faces the greatest internal challenges as his so-called faithful gather in Birmingham next week. Tavish Scott is Liberal Democrat MSP for Shetland