Political analysts say that if his Labour Party loses more than 300 council seats in London and other big urban areas to the opposition Conservatives and Liberal Democrats, it could ratchet up the pressure for him to stand down.

Thursday's polls -- hard on the heels on one of the toughest weeks for his nine-year-old government -- will be the first ballot-box test of Blair's popularity since he led Labour to a third straight general election win in May last year.

"It's a huge publicly funded opinion poll, but there will be judgements made about Tony Blair and his future," said political scientist Tony Travers at the London School of Economics.

"If the results were to be cataclysmic for the Labour Party, then clearly it would put greater pressure on Tony Blair."

This has certainly been a rough week for Blair -- and not just because opinion polls are finding support for Labour at its lowest levels since it swept to power in May 1997.

Home Secretary Charles Clarke faced calls to resign after he acknowledged that more than 1,000 convicts of foreign nationality were not considered for deportation -- as they should have been -- after their release.

Clarke twice offered to resign, but Blair refused to accept, insisting he was the man to see through changes to deal with one of the core issues in the local elections -- law and order.

Nurses meanwhile heckled Health Secretary Patricia Hewitt for she suggested that the cash-strapped, free-care-for-all National Health Service was having "one of its best years ever" -- just as it contemplates layoffs.

Then pugnacious deputy prime minister John Prescott went to ground when he admitted that he had cheated on his wife for two years in favour of a secretary 24 years his junior.

Lurking in the shadows are unresolved allegations -- now the subject of police inquiries -- that Labour and other political parties offered places in the House of Lords and other honours to wealthy supporters.

The most recent ICM opinion poll, released April 21, put Labour support at a 19-year low of 32 percent -- way down from 41 percent in 2001 and 35 percent a month prior to last year's general election.

If Blair has jitters, however, he is not showing them.

"In this business ... there's no problem that isn't a crisis, no difficulty that isn't a catastrophe, no week that isn't going to end up being the most terrible thing that's ever happened," he said this past week.

"You do the job, you get on with doing the job," he told BBC television as he campaigned for Labour councillors in east London.

At stake Thursday are 176 city, town, borough and other councils, with a total of 4,360 seats up for grabs.

John Curtice, professor of politics at Strathclyde University in Scotland, reckons that heavy Labour losses are "almost inconceivable" because the party fared so badly in past local elections that it has little more to lose.

Speculation over Blair's future has been running at fever pitch since he announced -- unusually for a serving prime minister -- that he would not serve more than a third term in office.

Guessing how soon he might go -- and he could wait until 2010 if he wants to drag it to the limit -- has become a popular parlor game for Britain's chattering classes.

Watching closely, but keeping a low profile, is Blair's finance minister and long time heir apparent, Chancellor of the Exchequer Gordon Brown, who enjoys a higher rating with the electorate.

Blair is also helped by the fact that the Tory and Lib Dem leaders, David Cameron and Sir Menzies Campbell, are both new to their jobs, with most voters still not yet sure what to make of them.

Cameron in particular has been busy styling himself as a youthful environmentalist -- going so far as to ride a dog sled in Norway to draw concern to global warming -- to reinvent the Conservatives as progressives.

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