By any conventional standards this should be a moment of high danger for Mr Tony Blair. Instead today's elections in England, Scotland and Wales seem likely to prove yet another high-point in Mr Blair's continuing ascendancy - confirmation, were it needed, of the enduring popularity both of the Prime Minister and of his New Labour creation.

While most attention is focused on the history-making events in Scotland and Wales, some 13,000 seats are also up-for-grabs in elections for 362 councils across the country.

These elections represent a re-run of the 1995 contests which delivered the Conservative Party's worst-ever performance this century. Two years after the general election massacre - with the arguable benefits of a new leader, and armed with the makings of a potentially decent campaign against government "stealth" taxes, and its "constitutional vandalism" - the former ruling party should be anticipating mid-term evidence of a substantial and sustained recovery.

Instead, Conservative Central Office is playing-down expectations - not the better and more convincingly to trumpet real and guaranteed achievement - but in the fearful knowledge that today's showing could put the party leader, Mr William Hague, on notice.

Local government experts predict that the Tories could gain up to 1,400 seats, win back control of some 30 authorities, and send some Labour strongholds into "no overall control". But - against the loss of 2,000 seats, and a 25 per cent share of the vote in 1995 - Mr Hague, in real terms, needs to do better if he is to convince an increasingly doubtful party to stick with him.

A marginal improvement on the party's 1997 take of 31.07 per cent of the vote, might win the Tory leader a temporary respite. But the European elections, with all the risks of further public division, have still to come. Even as the party's candidates made their final pitch for votes yesterday, the talk was that Mr Michael Portillo would not be available to come to the aid of the leader and serve as party chairman. Still more ominously, there was renewed speculation that the former chancellor, Mr Kenneth Clarke, would be prepared to seek the leadership should Mr Hague be ousted this summer.

Labour's biggest danger, it would appear, is apathy and complacency. Or, as the party's spin doctors would have it, "the politics of contentment". That could be a particularly potent danger in the elections for the Welsh National Assembly, where widespread indifference to devolution may be contributing to a late surge by Plaid Cymru. Labour will, of course, command a comfortable majority in the 60member Assembly. However, party chiefs will be alarmed by the latest poll finding, showing the nationalists doubling their support from 1997, with Labour support down from 55 per cent then to 47 per cent now.

Perversely, an under-performance by Labour, at any rate in Carmarthen East and Dinefwr, could save the party the embarrassment of seeing Mr Alun Michael - Secretary of State, and Mr Blair's choice for First Secretary - denied a seat in the Assembly.

Mr Michael, a quintessential Blairite, had planned to continue making his way up the Westminster ladder until Mr Ron Davies' "moment of madness" on Clapham Common forced a vacancy at the Welsh Office. Mr Michael, with Mr Blair's help, won the subsequent leadership battle against the activists' choice, Mr Rhodri Morgan.

However, with individual constituency candidates already selected, he was forced to rely on election via the party's regional list, on the second top-up vote. His chances of election would be greatly helped should Labour lose the directly elected seat in Carmarthen East and Dinefwr. But while Plaid is pressing hard, there have been consistent reports that Mr Davies (who anticipates a seat in the Welsh Executive, at least) and Mr Morgan, have been pulling out all the stops to ensure that doesn't happen.

A third contest for the Welsh leadership is emphatically not part of Mr Blair's game plan. But, as with so much else about the devolution "process", it may prove beyond his control.

The leadership in Scotland - both personal and party wise - is not, and never has been, in any real doubt. While Labour can fully expect reward for having delivered the first Scottish Parliament in 300 years, party chiefs would be genuinely astonished to find Mr Donald Dewar, the putative First Minister, tomorrow commanding an overall majority at Holyrood.

Naturally aiming to maximise the party's vote, Mr Dewar spent the dying hours of the campaign denying that he is planning a formal coalition with the Liberal Democrats. The denials of the Deputy Prime Minister, Mr John Prescott, were altogether more believable. Old Labour by instinct, he has little interest in fanciful talk of pluralism and inclusivity. Should the need arise, however, Mr Blair's will be the defining view.

The Liberal Democrats, of course, are perfectly capable of pricing themselves out of a deal. In that event, if Labour comes in close to 60 of the 129 seats, Mr Dewar could proceed to form a minority administration - with the tacit approval of Mr David McLetchie's Tories.

The already fully-devolved Tories will make the protection of the Union their guiding principle in the new parliament, which is set to reflect the reality of Scotland's unionist majority.

Earlier excited talk about the SNP running neck-and-neck with Labour will naturally see attention focused on how well, or how badly, Mr Salmond's party fares. The conventional wisdom is that securing 40 plus seats should remove any threat to his position. That said, a leadership challenge - or a split further down the line - could not be ruled out. Many of the party's fundamentalists have long-been suspicious of Mr Salmond's gradualist approach to the issue of Scottish independence. But that would surely be to postpone the party's arrival in the big league.

Long before Mr Ron Davies coined the phrase, Mr Salmond understood better than most the concept of devolution as "a process" rather than "an event". For all his denials, some who have watched him closely over the years remain convinced his strategy always presupposed an initial Labour victory, leaving the SNP free to enjoy the luxury of official opposition, while Scottish Labour discovers the contradictions and tensions inherent in the new relationship with London.

In the coming months, of course, that will be the real story of today's historic elections. Two years ago, in a desperate last-fling of the unionist card, John Major told Britons they were "sleepwalking into constitutional disaster". This week David Marquand, politician-turned-academic, put it differently. Britain, he said, was "sleepwalking towards a revolution".

Mr Blair's constitutional reforms are taking Britain into wholly uncharted waters. At the very least, as commentator Peter Kellner puts it, we are witnessing "the end of the United Kingdom as a nation state whose government exercises total sovereign power within its borders".

It may be, as one Tory historian argued yesterday, that, in "a perversely British way" the new arrangements might "bed down and work, despite their inherent contradictions." But they may not. Nobody, Mr Blair included, can foretell. But what we can say with certainty is that - if today's mid-term contest gives Mr Blair cause for further celebration - the real test will come when he discovers that he cannot devolve power and retain it, and that he cannot expect either always to be on the winning side.