Labour is celebrating a clean sweep in three parliamentary by-elections in Rotherham, Middlesbrough and Croydon North.
But the celebrations were maybe bigger at the UK Independence Party, which took second place in the two northern seats and recorded its best ever by-election result in Rotherham, where its candidate secured 21.8% of the vote.
The Liberal Democrats held onto third place behind Ukip in Middlesbrough, but finished fourth and lost its deposit in Croydon and suffered a woeful eighth place in Rotherham, where its candidate Michael Beckett lost his deposit and limped in behind not only Labour, Ukip, the British National Party, Respect and the Conservatives but also the English Democrats and an Independent.
The result led Labour MP Toby Perkins tweeting that Nick Clegg's party is heading for "extinction", writing: "Have Lib Dems seriously come eighth in Rotherham by-election? They must pull out of this damaging coalition or face extinction - simple."
It was a dismal night for both coalition parties, with Conservatives slumping to fourth in Middlesbrough and fifth in Rotherham.
For Ukip leader Nigel Farage, the results marked "big progress" just a fortnight after his party recorded its previous best by-election result of 14.3% in Corby.
His party was boosted in Rotherham by the controversy which blew up during the by-election campaign when social workers removed three children from foster parents because the couple were members of Ukip.
In Middlesbrough, the eurosceptic party moved up from sixth position in the 2010 general election to second with 11.8% of votes.
"Whichever way you look at it, Ukip is on the rise," said Mr Farage.
Speaking after her victory, Rotherham's new Labour MP Sarah Champion urged the Government to get the town "back to work".
"I've never stood for election before but when I see the damage David Cameron is doing to Rotherham I cannot stand and watch," she said.
Thursday's by-elections in Middlesbrough and Croydon North were triggered by the deaths of long-serving Labour MPs Sir Stuart Bell and Malcolm Wicks, and by the resignation of Rotherham's Denis MacShane in the wake of a highly critical report on the former Labour MP's parliamentary expenses.
Ms Champion's campaign was also hit by a row with party activists who favoured a local councillor as candidate.
But she secured a comfortable majority of 5,218 on a turnout of 33.6% to become the first female MP for a South Yorkshire seat which has been Labour since 1933. Her 24.5% margin of victory was little reduced from the 27.9% recorded by Mr MacShane in the general election.
In Middlesbrough, Labour's Andy McDonald enjoyed a massive 48.7% margin of victory over Ukip's Richard Elvin, well up on Sir Stuart's 26% lead in 2010.
The result saw a collapse in support for both coalition parties, which between them took 35% of votes in the Teesside town in 2010 but just 16% on Firday.
Mr McDonald, a solicitor who was born in Middlesbrough and served on the local council, said the result was a message to the coalition from "working families who are having their budgets squeezed, young people who are struggling to find their first job and the millions ignored by this Tory-led Government which thinks the priority is to cut tax for millionaires".
In Croydon North, Labour's Steve Reed scooped a comfortable 47.9% lead - well up on the 31.9% enjoyed by Mr Wicks in 2010 - and finished with 15,898 votes, ahead of Tory Andy Stranack on 4,137.
Mr Reed said the people of the constituency, in suburban south London had sent a "clear message" to the Prime Minister.
"David Cameron needs to listen," he said. "People are hurting because his economic policies are not working. He must change course on the economy."
Turnout in all three polls was relatively depressed, at 33.6% in Rotherham, 25.9% in Middlesbrough and 26.4% in Croydon North, but did not sink to the lows of under 20% seen in the Police and Crime Commissioner elections earlier this month.
Farage later said: "This is Ukip's most impressive result in Westminster elections so far.
"Jane Collins' 21% in Rotherham was our best ever score and this is backed up by 11% in Middlesbrough and coming third in Croydon North. This follows our stunning result in Corby a few weeks ago.
"The political establishment is just going to have to wake up to the fact that Ukip is here and here to stay as a significant and rising mainstream part of British politics.