Mr William Hague will fly the Union Flag today as he battles to avoid a Tory "meltdown" in England and a second successive wipe-out in Scotland and Wales.
At the start of a potentially historic election week for the United Kingdom, Mr Hague is also expected to open up a clear difference between the Conservatives and Labour over their attitude to the constitutional position of Northern Ireland.
Mr Charles Kennedy, meanwhile, has cast his Liberal Democrats to the left of Labour in a clear pitch for support among "heartland" Labour voters disillusioned with the first-term performance of the Blair government. While accepting it would be "a tall order" for the Liberal Democrats to win more seats than the Conservatives, Mr Kennedy said his party could provide the "ethical" opposition to Labour in the next parliament.
He made his move as the Conservatives launched an eleventh-hour bid to halt the predicted Labour landslide, with an appeal to voters to "burst" Mr Tony Blair's bubble and "take the smile" off his face.
However, the Prime Minister yesterday continued his assault on poll predictions, insisting talk of a Labour landslide was "pie in the sky". He was backed by the Chancellor, Mr Gordon Brown, who accused the Tories of "a desperate, cynical, last-minute attempt" to deter people from voting on Thursday.
Europe and nationhood are certain to play strongly in the final three days of campaigning as Labour and the Conservatives appeal to their supporters to do their patriotic duty on polling day.
The Conservative Party chairman, Mr Michael Ancram, returned to the euro theme yesterday, claiming Britain's continued existence as an independent nation would be lost if Labour won the election.
And Mr Hague will cast his as the only true party of the union, when he flies to Perth to try to boost Scottish Conservatives who are currently languishing in the polls on a mere 13 per cent.
The Shadow Northern Ireland Secretary, Mr Andrew Mackay, last week reaffirmed Conservative support for Mr David Trimble's approach to the full implementation of the Belfast Agreement. And despite declared worries about spiralling costs, and the anonymity provisions for service personnel, Mr Hague yesterday told the BBC that the Saville Inquiry into the events of Bloody Sunday would go ahead in the event of a Conservative government being elected this Thursday.
However, in Perth this evening Mr Hague will question Labour's "unionist" credentials. Specifically he is expected to say that only the Conservatives are fighting the election prepared "unashamedly and wholeheartedly to make the case for the United Kingdom" - and that his party alone offers a British government fighting "to value and include Northern Ireland within the United Kingdom".
Mr Hague will also tell his Scottish supporters that devolution is not about "taking orders from London", but "standing up and fighting for what's right for Scotland" while jealously guarding its position within the UK.
His latest campaign trip to Scotland comes amid reports that key figures in the Scottish Tory leadership believe electoral recovery there may require them to forge an organisational and political identity effectively independent of the party in England.
The Sunday Times yesterday quoted a source close to the Conservative leader in the Scottish Parliament, Mr David McLetchie, as saying: "Events tend to make decisions for you. Let's see how the landscape looks on Friday morning."
Mr Blair, meanwhile, continued to stamp on suggestions that the election was already in the bag for Labour.
"What the Conservatives are trying to do is simply to get people to stay at home or vote Conservative, not because of what they stand for or believe in but simply to suppress the so-called Labour majority that hasn't even happened", he told a caller on IRN's Call the Leader phone-in.
Mr Brown echoed Mr Blair's message to Labour voters, telling the GMB union conference in Brighton the Conservatives had given up on the arguments and were now simply trying to generate voter apathy.
"To win the battle against child and pensioner poverty and for schools and hospitals," declared Mr Brown, "first we must defeat not just political conservatism, but another form of conservatism - and more insidious - cynicism."
He continued: "The Tories are trying to make people believe that governments can never make a difference, that politics can never be a force for good, that a vote for anything positive doesn't really matter."