LONDON — British Prime Minister Gordon Brown yesterday faced a desperate battle to restore his authority after a second election rout in less than a month that dealt another blow to his shaky grip on power.
Just three weeks after his governing Labor Party suffered its worst local election results in 40 years, the main opposition Conservative Party seized a by-election victory in the Labor stronghold of Crewe and Nantwich.
Although a Conservative Party, or Tory, win in the northwest England seat was predicted, the size of the "swing" to the center-right party — nearly 18 percent — and the margin of victory by Edward Timpson in Thursday's vote took many by surprise.
One analyst even calculated that a similar-sized swing in a general election would give the Conservatives nearly 300 more members of Parliament than Labor, although that is unlikely.
But the scale of the by-election win — the Tories' first since 1982 and first in opposition since 1978 — plus its psychological effect will concern sitting Labor members of Parliament with slimmer majorities than the 7,078 Mr. Timpson overturned.
"Be in no doubt," said British Broadcasting Corp. political editor Nick Robinson. "If [Tory leader] David Cameron becomes prime minister, many will look back at the vote in Crewe and Nantwich as the moment they first believed it was possible.
"Not only is this the first Tory by-election gain from Labor in 30 years, it is on a swing that matches those secured by [former Tory leaders] Ted Heath and Margaret Thatcher before they reached Number 10 [Downing Street]."
Other commentators also talked of a tipping point, increasing the pressure on Mr. Brown and reigniting speculation of a leadership challenge by the time Labor holds its annual conference in September.
Labor's leadership election rules, which require any contender to obtain the support of 71 members of Parliament, could make this difficult, however.
Mr. Brown said yesterday the defeat was "clear and unequivocal" but said the public wanted the government to address the economic challenges ahead and he was the man to do it.
Mr. Cameron said it was "the end of New Labor," the project spearheaded by Mr. Brown and his predecessor Tony Blair in the mid-1990s to move the divided left-wing party to the center ground.
But he refused to say whether the win meant the Tories, written off before Mr. Brown's popularity began plummeting seven months ago, were now on course to regain power, vowing to build on the new "broad coalition for change."
There are suggestions the Tories will seek to capitalize on the win by calling an early by-election in Henley, the affluent seat south of Oxford, south central England, due to be vacated by new London Mayor Boris Johnson.
Mr. Brown's predicament was dire going into the vote, with Labor at record lows in the opinion polls and after outrage at the government's abolition of the lowest rate of income tax, which hit the country's lowest earners.
The result suggests voters were unmoved by his hastily prepared compensation package, as rising fuel and food costs and falling house prices begin to bite.