Few MPs could have carried it off, but Mr Dewar is one of a rather exclusive club of parliamentarians, respected by political friend and foe. He defies most of the expectations of modern politicians: Dewar is one member of the Shadow Cabinet not yet seen in a designer suit and is the antithesis of the chief whip figure immortalised by the fictional Francis Urquhart.
As a long-time Labour right-winger now in charge of party discipline one would expect him to provoke the hostility of the left. Not so. "I won't hear a bad word said of Donald," said one bolshie Labour left-winger last week before delivering a vicious broadside against the party's modernisers.
Other colleagues offer adjectives such as "honourable", "straight" or "trustworthy" that seem to pre-date the vocabulary of a cash-for-questions Commons. That, perhaps, explains the genuine air of outrage from Mr Dewar when Conservative skulduggery over the fisheries vote was revealed last week. Perplexed by the size of the Tory majority, the Chief Whip and his deputy, Nick Brown, stayed into the night checking lists. Gradually it began to appear that the Tories had offered the same MPs as "pairs" to Labour as they had to the Liberal Democrats. Thus the Government had taken six opposition votes out for the price of three of its own.
To check, Mr Dewar tried to contact his Liberal Democrat counterpart, Archy Kirkwood, who did not hear his pager (back in his London flat Mr Kirkwood was wearing headphones and playing the guitar to an orchestral soundtrack). So, at 1am on Tuesday morning, in the spartan Labour whips' office, the Chief Whip was heard fuming in his dour Glasgow tones: "I just do not believe this".
As one colleague put it: "You or I would hardly be surprised that the Tories were cheating, but Donald believed that they would ultimately behave honourably. To him this was extreme sharp practice, rather like burglary."
Born in 1937, Donald Dewar was brought up in a well-to-do enclave of pre-war Glasgow. His father, Dr Alasdair Dewar, was a consultant dermatologist and the family lived in a large Victorian house by Kelvingrove Park. Dewar senior was a cultured man with an impressive collection of early-20th- century Scottish colour paintings (his son inherited the interest in painting). Educated at prep school and Glasgow Academy, a day public school, Donald progressed to Glasgow University where he took an MA in history, switching to law. He was at university for six years, the later three concurrent with a legal apprenticeship and, like the majority of Scottish students in those days, lived at home. Contemporaries visited there often. This was the early Sixties but neither Dewar nor his native city were really swinging. The Liberal Democrat MP Menzies Campbell, a university contemporary, remembers social life revolving around "whisky and the socialist millennium rather than pot and free love". Dewar's nickname was "the gannet" because of his ability to eat without losing his rake-like figure. He was also renowned for his poor spelling; John Smith, a close friend and the future Labour leader, used to say that Dewar once spelt Garibaldi four different ways in a history essay getting it wrong each time. University allowed Dewar to mix with the rising political stars of his generation many of whom, like Smith and Campbell, became lifelong friends. In debate he could be aggressive and spiky, showing a reluctance to tolerate fools which has not completely disappeared. President of the Union and chairman of the Labour club, the young Dewar was Gaitskellite and pro-devolution.
Even before he could qualify as a solicitor Dewar had been selected for the Tory-held seat of Aberdeen South, then held by the junior Scottish Office minister Lady Tweedsmuir. By chance the MP visited Glasgow University and, when introduced at a reception to her opponent, offered the view that she didn't t hink that the young Dewar would "need to interrupt his studies". Dewar had the last laugh a couple of years later when he unexpectedly unseated her in the 1966 election. Within a year Dewar became parliamentary private secretary to Anthony Crosland, the closest he has yet come to government office.
But 1970 proved to be a bad year. Out for six weeks with crippling back trouble, he lost his seat in the election and his marriage broke up. As one friend put it: "Any one of those three disasters would be difficult to cope with, Donald had all three in a year." He had married Alison McNair, a university friend, in 1964 and when they parted the couple had two small children. They divorced in 1973 and she remarried, to another leftish Scottish lawyer and Glasgow University graduate, Derry Irvine, now the Shadow Lord Chancellor and a friend of the Labour leader. Inevitably the Dewar/Irvine relationship was difficult and the two men are said to have spoken for the first time in more than 20 years at the funeral of their mutual friend, John Smith.
Politically, most of the 1970s were wilderness years. Out of parliament, Dewar returned to law becoming Reporter to the Children's Panel, the Scottish court system for juvenile offenders. By chance he ran into a university contemporary and stalwart of the Conservative Party, Ross Harper, took up an invitation to join his law firm and rapidly became a partner. But Dewar kept a hand in politics, hosting a 7pm Friday-night discussion programme on Radio Clyde. After eight years he was back at Westminster, a by-election victor for the Garscadden seat he has since represented. By now John Smith, his old ally and rival, was Cabinet-bound, but Dewar had only a year to go before opposition beckoned.
Much of the Thatcher period - another, different, political wilderness - was spent as Shadow Secretary of State for Scotland, an experience which proved Dewar's ability and resilience. A co-founder of the right-wing Solidarity movement (formed when others left to join the SDP), he faced pressure from the nationalists, the Scottish TUC and from elements of an occasionally fractious party. To add to those difficulties, the job has an extremely broad brief. As one ally put it: "You go to a press conference to discuss criminal justice reform and you are asked about unemployment figures, forestry policy in the north-west, fisheries regulations and a factory closure in Kirkcaldy. You can't duck any of them because they are your responsibility."
After the election he served as Social Security spokesman before being moved last year, against his own expectations, to become Chief Whip. Dewar has impressed, revitalising a part of the Labour operation widely seen as a professional dead-end. He has imposed a new, tough disciplinary code while keeping most of the left on board. And he has proved the power of straight-talking. As one friend put it: "He never says anything for the purpose of pleasing. But if he thinks you are wrong he has a nice way of saying it. It's rather like talking to your father after you've misbehaved."
Some believe Dewar lives up to the caricature of the dour Calvinist Scot. He can be gauche on first meeting but the recluse tag is misleading. In the company of friends, politicians or journalists he is a practised raconteur with a self-effacing, dry wit. He has a wide and varied circle of friends and is rarely in of a Friday or Saturday night.
Yet he remains a bit of a loner. He has not remarried and friends say he is skilled at "side-stepping" female advances. Bachelorhood suits him; he is a voracious reader and his Victorian home in Glasgow's West End (about a mile and a half from where he grew up) is littered with books. Fellow MPs on a delegation to Scandinavia several years ago were surprised to discover that he did not possess a coat. According to a friend he still has not acquired one, complaining that his last one was "stolen".
Living alone he can indulge his interests in books, theatre, football (no particular team) and history. He is, for example, an expert on the split between the established church and the Free Church in the 19th century. His dedication to the party is undisputed. He will travel mid-week to Scotland to address a party meeting and return to Westminster by sleeper (he dislikes flying).
Even with the current unstable parliamentary position he is unlikely to err on the side of optimism. "You do realise," said one friend last week mimicking Dewar's Glaswegian tones, "we're only 27 points up in today's opinion poll." Tony Blair will not get an upbeat assessment of his prospects of bringing down the Government.
During a lengthy political career, Dewar has stuck to his early convictions. Passionately pro-devolution, he was one of only two MPs to defend the policy at the Scottish party conference in Ayr in 1968 when it was deeply unfashionable. And, as an old right-winger, it is appropriate that Dewar should be spending some of his Christmas break chez Roy Hattersley.
At 59, Dewar is not seen as a potential Labour leader, but his place at the party's top table is well established, and there is much speculation about the role he will play if Mr Blair wins the election. He looks capable of occupying almost any Cabinet post. He might stay as Chief Whip since he is enjoying life at the political centre. Another possibility is Leader of the House in charge of the legislation for a Scottish parliament, which would be a fitting monument to his political career.
Friends play down the parallel between Dewar's position and the elder statesman roles played by Willie Whitelaw or Douglas Hurd to the last two Tory Prime Ministers. In private, Mr Blair is not so dismissive of the analogy. After years in opposition and a life touched by political and personal ill-fortune, Donald Dewar's time may be coming.