By Nick Assinder
Political correspondent, BBC News website
Tory Bob Neill and Labour's Rachel Reeve after the Bromley result
There can be no clearer indication of the difficulties currently facing Tony Blair and his government than the results in the Bromley and Blaenau Gwent by-elections.
And the signs are seriously bad, with the party failing to regain Blaenau Gwent and plunging into fourth place behind the Liberal Democrats and UKIP in Bromley and Chislehurst.
The results are bound to result in renewed claims that Mr Blair has turned from an electoral asset to a liability and increase pressure on him to announce a timetable for his departure.
But, while it may have been a disastrous night for Labour, there was also a sharp kick in the pants for David Cameron's Tories.
They came dangerously close to losing the once safe-as-houses seat of Bromley to a sensational Liberal Democrat surge.
Blow to Blair
That result will be a huge relief to Lib Dem leader Sir Menzies Campbell, who has been struggling to underpin his leadership, but it also gives a boost to UKIP whose Nigel Farage put himself firmly on the by-election map.
Labour will use the Bromley result to claim Mr Cameron's leadership is failing, but it is Mr Blair who has the most to worry about after a night of setbacks.
Labour Party bosses had been quietly hopeful they could take back the rock solid seat in Wales, which had previously returned both Nye Bevan and Michael Foot to Westminster but which was lost to independent, former Labour man, Peter Law last year.
In a bitter blow, the party was forced to concede in both the Westminster and Welsh Assembly polls as voters showed no sign they were ready to return to the fold.
Labour may try to claim the disaster was a result of continuing local resentment over the women-only shortlist row which drove Mr Law into going independent in 2005.
But the failure to regain such a dyed-in-the wool Labour seat also speaks volumes about the depth of the disenchantment with the government in its heartlands.
And it comes hard on the heels of damaging claims by former Home Secretary Charles Clarke that Mr Blair has lost authority, purpose and sense of direction.
Ray of sunshine
Meanwhile, in true-blue Bromley, Labour watched as it slumped into fourth place behind both the Liberal Democrats and, worse for Mr Blair, UKIP.
There was never a chance Labour could win this seat, but this humiliation is exactly the result the party was desperate to avoid.
However, in a shock ray of sunshine around the dark clouds, Labour watched the Tory vote slide - a hugely disappointing outcome for Mr Cameron whose own leadership style will now come under scrutiny.
Tory bosses may suggest the result was caused by the local party's insistence on choosing an old-style candidate rather than one from Mr Cameron's A-list of youthful modernisers.
But Mr Cameron will struggle to explain just how his apparently reviving party failed to hold on to its massive majority in the seat and come so close to a disaster.
Meanwhile, the Liberal Democrats will once again claim they really are part of a three-party system and able to scare both the other two big parties.
The performance comes after February's shock Lib Dem victory over Labour in the Dunfermline and West Fife by-election.
It will be particularly encouraging to Sir Menzies Campbell whose leadership honeymoon ended almost before it began, with poor Commons performances and doubts raised about his age and ability to meet the challenges of the leadership.
But it is Tony Blair and his supporters who will be counting the cost of these results over coming days and weeks.
The prime minister has suffered a nightmare few months, with Labour slipping behind the Tories in the polls and suffering a series of political setbacks, from the cash-for-peerages row through the John Prescott affair, to the string of Home Office crises.
And all this against a background of continuing questions over the prime minister's retirement plans and the timing of the expected handover to Gordon Brown.
These results will further intensify the pressure on the prime minister to clarify his intentions, with this September's party conference in Manchester being looked to as the most likely time for that.