Alex Salmond, the First Minister, and John Mason, a well-informed and determined councillor, have converted Labour's third-safest seat in Scotland into SNP sensation No5.
It had looked so unlikely right up to the close of polls. The fear was that the East End's heart remained Labour, no matter how badly it performed at Westminster, or how ineffective it was at tackling problems on the ground. Labour, ran the argument, was as ingrained in the Glasgow working-class as football and religion.
But asked to send a message to the Prime Minister about the soaring cost of living, the people rejected their party of habit, of their parents and probably their grandparents, and backed the Nats. What a mighty earthquake they have triggered.
Now no Labour MP is safe. This was the party's 25th-safest seat in the UK. The party faces destruction whenever the general election is called – and there has to be one by June 2010.
Mr Salmond visited 12 times. Gordon Brown claimed Prime Ministerial exemption from by-elections and went to Iraq and Israel. In doing so, he insulted his fellow Scots – and sent out a message: he was scared. Look how they have repaid him. The people of Glasgow East have sparked the endgame in his premiership – Labour back-benchers will be queuing up to show him the door.
Nationalists never tire of recalling how Winnie Ewing's victory in Hamilton in 1967, with a 1,799 majority over Labour, started the Nationalists' ball rolling.
Then it was Margo MacDonald, who won Glasgow Govan with a narrow 571 majority over Labour in 1973. She was unable to hold the seat at the following year's general election.
Govan retained its place in Nationalist folklore when in 1988 Jim Sillars, Ms MacDonald's husband and a former Labour MP, stole it from Labour's clutches in a by-election prompted by the resignation of Bruce Millan. Mr Sillars, a streetwise campaigner, achieved a 33 per cent swing that gave him a 3,554 majority over the hapless Labour candidate, Bob Gillespie.
Then in 1995, the SNP's Roseanna Cunningham stole Perth and Kinross from the Conservatives following the death of the sitting MP, Sir Nicholas Fairbairn. With the election falling mid-term for John Major's crisis-hit administration, Ms Cunningham achieved an 11.5 per cent swing and a 7,311 majority – but over Labour, as the Tories were pushed into third place.
The signs were there, and not only at Holyrood. Labour came within 556 votes of losing Hamilton South in 1999 – despite defending a majority of almost 16,000 – when George Robertson stood down to become a peer and secretary-general of Nato.
Labour also suffered a scare from the Nationalists in 2000, when Eric Joyce was elected with a majority of just 705, despite Labour defending a 14,000 majority from the 1997 general election landslide that brought Tony Blair into Downing Street.
Mr Salmond will struggle to contain his smile. He gambled his personal reputation – and won handsomely. Do they feel the tremors at No10? There's not the slightest doubt about that.
THE TURNOUT: Sunshine brings out 42% surge of voters
THE polls closed last night amid signs of a higher-than-expected turnout of just over 42 per cent.
A survey at 9pm had suggested a level of 41 per cent, a full hour before polls closed.
That compares with 48 per cent at the 2005 General Election and would be slightly higher than the high 30s suggested by bookmakers' odds during the campaign.
Signs of a strong turnout emerged earlier as the sun shone on voters going to the polls.
The 76 ballot boxes from 40 polling places were counted at the Tollcross leisure centre.
The total number of electors eligible to vote was 62,051, and some 3,911 of these had registered for a postal vote.
Labour sent out around 400 activists to bolster their support in the morning and said that early indications had pointed to a strong turnout.
In Crewe and Nantwich in May, which was won by the Conservatives, turnout was high for a by-election at 58.2 per cent.
At the Haltemprice, East Yorkshire, by-election, won by Tory David Davis earlier this month, the turnout was just over 34 per cent.